290 files changed, 7587 insertions, 5836 deletions

diff --git a/lib/classes/ActionMenu.php b/lib/classes/ActionMenu.php
index 0822f72..25351ce 100644
--- a/lib/classes/ActionMenu.php
+++ b/lib/classes/ActionMenu.php
@@ -410,7 +410,7 @@ class ActionMenu
         $rendering_mode = $this->rendering_mode;
 
         if ($rendering_mode === null) {
-            $rendering_mode = $this->countActions() <= Config::get()->ACTION_MENU_THRESHOLD
+            $rendering_mode = $this->countActions() <= 1 // Config::get()->ACTION_MENU_THRESHOLD
                             ? self::RENDERING_MODE_ICONS
                             : self::RENDERING_MODE_MENU;
         }
diff --git a/lib/classes/AdminCourseFilter.class.php b/lib/classes/AdminCourseFilter.php
index da8ce54..f643e09 100644
--- a/lib/classes/AdminCourseFilter.class.php
+++ b/lib/classes/AdminCourseFilter.php
@@ -28,6 +28,8 @@
 class AdminCourseFilter
 {
     static protected $instance = null;
+
+    /** @var SQLQuery|null  */
     public $query = null;
     public $max_show_courses = 500;
     public $settings = [];
@@ -84,21 +86,11 @@ class AdminCourseFilter
                 return $a['Institut_id'];
             });
         } else {
-            //We must check, if the institute ID belongs to a faculty
-            //and has the string _i appended to it.
-            //In that case we must display the courses of the faculty
-            //and all its institutes.
-            //Otherwise we just display the courses of the faculty.
 
-            $include_children = false;
             $inst_id = $GLOBALS['user']->cfg->MY_INSTITUTES_DEFAULT;
-            if (str_contains($inst_id, '_')) {
-                $inst_id = substr($inst_id, 0, strpos($inst_id, '_'));
-                $include_children = true;
-            }
             $inst_ids[] = $inst_id;
 
-            if ($include_children) {
+            if ($GLOBALS['user']->cfg->MY_INSTITUTES_INCLUDE_CHILDREN) {
                 $inst = Institute::find($inst_id);
                 if ($inst && $inst->isFaculty()) {
                     foreach ($inst->sub_institutes->pluck('Institut_id') as $institut_id) {
@@ -109,13 +101,10 @@ class AdminCourseFilter
         }
 
         if (Config::get()->ALLOW_ADMIN_RELATED_INST) {
-            $sem_inst = 'seminar_inst';
-            $this->query->join('seminar_inst', 'seminar_inst', 'seminar_inst.seminar_id = seminare.Seminar_id');
+            $this->query->where('seminar_inst', 'EXISTS (SELECT 1 FROM seminar_inst WHERE seminar_id = seminare.Seminar_id AND institut_id IN (:institut_ids))');
         } else {
-            $sem_inst = 'seminare';
+            $this->query->where("seminar_inst", "seminare.institut_id IN (:institut_ids)");
         }
-
-        $this->query->where('seminar_inst', "$sem_inst.institut_id IN (:institut_ids)");
         $this->query->parameter('institut_ids', $inst_ids);
 
         if ($GLOBALS['user']->cfg->MY_COURSES_SELECTED_CYCLE) {
@@ -196,6 +185,16 @@ class AdminCourseFilter
     }
 
     /**
+     * @param int|null $limit
+     * @return Course[]
+     */
+    public function fetchCourses(?int $limit = null): array
+    {
+        NotificationCenter::postNotification('AdminCourseFilterWillQuery', $this);
+        return $this->query->fetchAll(Course::class, $limit);
+    }
+
+    /**
      * Returns the data of the resultset of the AdminCourseFilter.
      *
      * @param string $order_by possible values name or number
@@ -206,16 +205,16 @@ class AdminCourseFilter
      */
     public function getCoursesForAdminWidget(string $order_by = 'name')
     {
-        $count_courses = $this->countCourses();
-        $order = 'seminare.name';
-        if ($order_by === 'number') {
-            $order = 'seminare.veranstaltungsnummer, seminare.name';
-        }
-        if ($count_courses && $count_courses <= $this->max_show_courses) {
+        try {
+            $order = 'seminare.name';
+            if ($order_by === 'number') {
+                $order = 'seminare.veranstaltungsnummer, seminare.name';
+            }
             $this->query->orderBy($order);
-            return $this->getCourses();
+            return $this->fetchCourses($this->max_show_courses);
+        } catch (OverflowException $e) {
+            return [];
         }
-        return [];
     }
 
 }
diff --git a/lib/classes/Assets.class.php b/lib/classes/Assets.php
index 928c47c..d4d792e 100644
--- a/lib/classes/Assets.class.php
+++ b/lib/classes/Assets.php
@@ -6,7 +6,7 @@
 # Lifter010: TODO
 
 /*
- * Assets.class.php - assets helper
+ * Assets.php - assets helper
  *
  * Copyright (C) 2007 - Marcus Lunzenauer <mlunzena@uos.de>
  *
diff --git a/lib/classes/AuthenticatedController.php b/lib/classes/AuthenticatedController.php
new file mode 100644
index 0000000..e051ffa
--- /dev/null
+++ b/lib/classes/AuthenticatedController.php
@@ -0,0 +1,32 @@
+<?php
+/*
+ * Copyright (C) 2009 - Marcus Lunzenauer <mlunzena@uos.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+class AuthenticatedController extends StudipController
+{
+    protected $with_session = true;  //we do need to have a session for this controller
+    protected $allow_nobody = false; //nobody is not allowed and always gets a login-screen
+
+    public function before_filter(&$action, &$args)
+    {
+        parent::before_filter($action, $args);
+
+        // Restore request if present
+        if (isset($this->flash['request'])) {
+            foreach ($this->flash['request'] as $key => $value) {
+                Request::set($key, $value);
+            }
+        }
+    }
+
+    protected function keepRequest()
+    {
+        $this->flash['request'] = Request::getInstance()->getIterator()->getArrayCopy();
+    }
+}
diff --git a/lib/classes/AuthorObject.class.php b/lib/classes/AuthorObject.php
index b3e98e3..f08622e 100644
--- a/lib/classes/AuthorObject.class.php
+++ b/lib/classes/AuthorObject.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +--------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// AuthorObject.class.php
+// AuthorObject.php
 //
 // Class to provide basic properties of an object in Stud.IP
 //
@@ -31,7 +31,7 @@ define("ERROR_CRITICAL", "8");
 
 
 /**
- * AuthorObject.class.php
+ * AuthorObject.php
  *
  * Class to provide basic properties of an object in Stud.IP
  *
@@ -136,4 +136,3 @@ class AuthorObject
         $class->resetErrors();
     }
 }
-
diff --git a/lib/classes/AutoInsert.class.php b/lib/classes/AutoInsert.php
index b2168cc..b5cc005 100644
--- a/lib/classes/AutoInsert.class.php
+++ b/lib/classes/AutoInsert.php
@@ -14,7 +14,7 @@
  */
 
 /**
- * AutoInsert.class.php
+ * AutoInsert.php
  * Provides functions required by StEP00216:
  * - Assign seminars for automatic registration of certain user types
  * - Maintenance of registration rules
diff --git a/lib/classes/AuxLockRules.class.php b/lib/classes/AuxLockRules.class.php
deleted file mode 100644
index 4d06ca2..0000000
--- a/lib/classes/AuxLockRules.class.php
+++ /dev/null
@@ -1,124 +0,0 @@
-<?
-# Lifter002: DONE
-# Lifter007: TODO
-# Lifter003: TEST
-# Lifter010: TODO
-/**
-* ZusatzLockRules.class.php - Sichtbarkeits-Administration fuer Zusatzangaben bei Teilnehmerlisten
-*
-* Copyright (C) 2006 Till Glöggler <tgloeggl@inspace.de>
-*
-* This program is free software; you can redistribute it and/or
-* modify it under the terms of the GNU General Public License
-* as published by the Free Software Foundation; either version 2
-* of the License, or (at your option) any later version.
-*
-* This program is distributed in the hope that it will be useful,
-* but WITHOUT ANY WARRANTY; without even the implied warranty of
-* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-* GNU General Public License for more details.
-*
-* You should have received a copy of the GNU General Public License
-* along with this program; if not, write to the Free Software
-* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
-*/
-
-/**
- * @deprecated since Stud.IP 5.3
- */
-class AuxLockRules
-{
-
-    static function _toArray($data)
-    {
-        return [
-            'lock_id' => $data['lock_id'],
-            'name' => $data['name'],
-            'description' => $data['description'],
-            'attributes' => json_decode($data['attributes'], true),
-            'order' => json_decode($data['sorting'], true)
-        ];
-    }
-
-    static function getAllLockRules()
-    {
-        $ret = [];
-        $db = DBManager::get()->query("SELECT * FROM aux_lock_rules");
-        while ($data = $db->fetch(PDO::FETCH_ASSOC)) {
-            $ret[$data['lock_id']] = AuxLockRules::_toArray($data);
-        }
-
-        return $ret;
-    }
-
-    static function getLockRuleById($id)
-    {
-        $stmt = DBManager::get()->prepare("SELECT * FROM aux_lock_rules WHERE lock_id = ?");
-        $stmt->execute([$id]);
-        $data = $stmt->fetch(PDO::FETCH_ASSOC);
-        return AuxLockRules::_toArray($data);
-    }
-
-    static function getLockRuleBySemId($sem_id)
-    {
-        $stmt = DBManager::get()->prepare("SELECT aux_lock_rule FROM seminare WHERE Seminar_id = ?");
-        $stmt->execute([$sem_id]);
-        $lock_rule = $stmt->fetchColumn();
-        if ($lock_rule) {
-            return AuxLockRules::getLockRuleById($lock_rule);
-        }
-        return NULL;
-    }
-
-    static function createLockRule($name, $description, $fields, $order)
-    {
-        $id = md5(uniqid(rand()));
-        $attributes = json_encode($fields);
-        $sorting = json_encode($order);
-        $stmt = DBManager::get()->prepare('INSERT INTO aux_lock_rules '
-                    . '(lock_id, name, description, attributes, sorting) '
-                . 'VALUES (?, ?, ?, ?, ?)');
-        $stmt->execute([$id, $name, $description, $attributes, $sorting]);
-        return $id;
-    }
-
-    static function updateLockRule($id, $name, $description, $fields, $order)
-    {
-        $attributes = json_encode($fields);
-        $sorting = json_encode($order);
-        $stmt = DBManager::get()->prepare('UPDATE aux_lock_rules '
-                    . 'SET name = ?, description = ?, attributes = ?, sorting = ? '
-                    . 'WHERE lock_id = ?');
-        return $stmt->execute([$name, $description, $attributes, $sorting, $id]);
-    }
-
-    static function deleteLockRule($id)
-    {
-        $stmt = DBManager::get()->prepare('SELECT COUNT(*) as c FROM seminare WHERE aux_lock_rule = ?');
-        $stmt->execute([$id]);
-        if ($stmt->fetchColumn() > 0) return false;
-
-        $stmt = DBManager::get()->prepare('DELETE FROM aux_lock_rules WHERE lock_id = ?');
-        return $stmt->execute([$id]);
-    }
-
-    static function getSemFields()
-    {
-        return [
-            'vasemester' => 'Semester',
-            'vanr' => 'Veranstaltungsnummer',
-            'vatitle' => 'Veranstaltungstitel',
-            'vadozent' => 'Dozent'
-        ];
-    }
-
-    static function checkLockRule($fields)
-    {
-        $entries = DataField::getDataFields('usersemdata');
-        foreach ($entries as $id => $entry) {
-            if ($fields[$entry->datafield_id] == 1) return true;
-        }
-
-        return false;
-    }
-}
diff --git a/lib/classes/Avatar.class.php b/lib/classes/Avatar.php
index 959523f..959523f 100644
--- a/lib/classes/Avatar.class.php
+++ b/lib/classes/Avatar.php
diff --git a/lib/classes/BreadCrumb.class.php b/lib/classes/BreadCrumb.php
index 73a2086..73a2086 100644
--- a/lib/classes/BreadCrumb.class.php
+++ b/lib/classes/BreadCrumb.php
diff --git a/lib/classes/Button.class.php b/lib/classes/Button.php
index 1c2c437..1c2c437 100644
--- a/lib/classes/Button.class.php
+++ b/lib/classes/Button.php
diff --git a/lib/classes/CSVArrayObject.class.php b/lib/classes/CSVArrayObject.php
index f075795..f075795 100644
--- a/lib/classes/CSVArrayObject.class.php
+++ b/lib/classes/CSVArrayObject.php
diff --git a/lib/classes/Color.class.php b/lib/classes/Color.php
index a9b4506..dcd68f5 100644
--- a/lib/classes/Color.class.php
+++ b/lib/classes/Color.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * lib/classes/Color.class.php - class to mix colors and convert them between different types
+ * lib/classes/Color.php - class to mix colors and convert them between different types
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -367,4 +367,4 @@ class Color {
         return [$H, $S, $L];
     }
 
-}
\ No newline at end of file
+}
diff --git a/lib/classes/Config.class.php b/lib/classes/Config.php
index 4d57f0f..c49a845 100644
--- a/lib/classes/Config.class.php
+++ b/lib/classes/Config.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * Config.class.php
+ * Config.php
  * provides access to global configuration
  *
  * This program is free software; you can redistribute it and/or
@@ -127,9 +127,14 @@ class Config implements ArrayAccess, Countable, IteratorAggregate
      */
     public function getValue($field)
     {
+        if ($this->fromEnv($field)) {
+            return $_ENV["STUDIP_CONFIG_{$field}"];
+        }
+
         if (array_key_exists($field, $this->data)) {
             return $this->data[$field];
         }
+
         if (isset($GLOBALS[$field]) && !isset($_REQUEST[$field])) {
             return $GLOBALS[$field];
         }
@@ -153,11 +158,8 @@ class Config implements ArrayAccess, Countable, IteratorAggregate
 
     /**
      * IteratorAggregate
-     *
-     * @todo Add Traversable return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         return new ArrayIterator($this->data);
     }
@@ -188,55 +190,40 @@ class Config implements ArrayAccess, Countable, IteratorAggregate
 
     /**
      * ArrayAccess: Check whether the given offset exists.
-     *
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return isset($this->$offset);
     }
 
     /**
      * ArrayAccess: Get the value at the given offset.
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         return $this->$offset;
     }
 
     /**
      * ArrayAccess: Set the value at the given offset.
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
         $this->$offset = $value;
     }
 
     /**
      * ArrayAccess: unset the value at the given offset (not applicable)
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
 
     }
 
     /**
      * Countable
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function count()
+    public function count(): int
     {
         return count($this->data);
     }
@@ -468,4 +455,15 @@ class Config implements ArrayAccess, Countable, IteratorAggregate
 
         return (string) $value;
     }
+
+    /**
+     * Returns whether the value was set from the environment.
+     *
+     * @param string $field
+     * @return bool
+     */
+    public function fromEnv(string $field): bool
+    {
+        return isset($_ENV["STUDIP_CONFIG_{$field}"]);
+    }
 }
diff --git a/lib/classes/CourseAvatar.class.php b/lib/classes/CourseAvatar.php
index 8c153a8..8c153a8 100644
--- a/lib/classes/CourseAvatar.class.php
+++ b/lib/classes/CourseAvatar.php
diff --git a/lib/classes/CourseConfig.class.php b/lib/classes/CourseConfig.php
index ad62be0..3ac5587 100644
--- a/lib/classes/CourseConfig.class.php
+++ b/lib/classes/CourseConfig.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * CourseConfig.class.php
+ * CourseConfig.php
  * provides access to course preferences
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/CronJob.class.php b/lib/classes/CronJob.php
index 1e7fb41..dee65e7 100644
--- a/lib/classes/CronJob.class.php
+++ b/lib/classes/CronJob.php
@@ -10,7 +10,7 @@
 
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// Cronjob.class.php
+// Cronjob.php
 //
 // Copyright (C) 2013 Jan-Hendrik Willms <tleilax+studip@gmail.com>
 // +---------------------------------------------------------------------------+
diff --git a/lib/classes/CronjobScheduler.class.php b/lib/classes/CronjobScheduler.php
index 67db94c..fbb5b66 100644
--- a/lib/classes/CronjobScheduler.class.php
+++ b/lib/classes/CronjobScheduler.php
@@ -10,7 +10,7 @@
 
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// CronjobScheduler.class.php
+// CronjobScheduler.php
 //
 // Copyright (C) 2013 Jan-Hendrik Willms <tleilax+studip@gmail.com>
 // +---------------------------------------------------------------------------+
@@ -132,35 +132,6 @@ class CronjobScheduler
     }
 
     /**
-     * Schedules a task for a single execution at the provided time.
-     *
-     * @param String $task_id    The id of the task to be executed
-     * @param int    $timestamp  When the task should be executed
-     * @param String $priority   Priority of the execution (low, normal, high),
-     *                           defaults to normal
-     * @param Array  $parameters Optional parameters passed to the task
-     * @return CronjobSchedule The generated schedule object.
-     */
-    public function scheduleOnce($task_id, $timestamp, $priority = CronjobSchedule::PRIORITY_NORMAL,
-                                 $parameters = [])
-    {
-        $schedule = new CronjobSchedule();
-        $schedule->type           = 'once';
-        $schedule->task_id        = $task_id;
-        $schedule->parameters     = $parameters;
-        $schedule->priority       = $priority;
-        $schedule->next_execution = $timestamp;
-
-        $schedule->store();
-
-        $task = $schedule->task;
-        $task->assigned_count += 1;
-        $task->store();
-
-        return $schedule;
-    }
-
-    /**
      * Schedules a task for periodic execution with the provided schedule.
      *
      * @param String $task_id     The id of the task to be executed
@@ -185,21 +156,21 @@ class CronjobScheduler
      *                            - 1 >= x >= 7 for "exactly at day of week x"
      *                              (x starts with monday at 1 and ends with
      *                               sunday at 7)
-     * @param String $priority   Priority of the execution (low, normal, high),
-     *                           defaults to normal
      * @param Array  $parameters Optional parameters passed to the task
      * @return CronjobSchedule The generated schedule object.
      */
-    public function schedulePeriodic($task_id, $minute = null, $hour = null,
-                                     $day = null, $month = null, $day_of_week = null,
-                                     $priority = CronjobSchedule::PRIORITY_NORMAL,
-                                     $parameters = [])
-    {
+    public function schedule(
+        string $task_id,
+        ?int $minute = null,
+        ?int $hour = null,
+        ?int $day = null,
+        ?int $month = null,
+        ?int $day_of_week = null,
+        array $parameters = []
+    ): CronjobSchedule {
         $schedule = new CronjobSchedule();
-        $schedule->type       = 'periodic';
         $schedule->task_id    = $task_id;
         $schedule->parameters = $parameters;
-        $schedule->priority   = $priority;
 
         $schedule->minute = $minute;
         $schedule->hour = $hour;
@@ -217,6 +188,24 @@ class CronjobScheduler
     }
 
     /**
+     * An alias for schedule for backwards compatibility.
+     *
+     * @see CronjobScheduler::schedule()
+     */
+    public function schedulePeriodic(
+        $task_id,
+        $minute = null,
+        $hour = null,
+        $day = null,
+        $month = null,
+        $day_of_week = null,
+        $priority = null,
+        $parameters = []
+    ) {
+        return $this->schedule($task_id, $minute, $hour, $day, $month, $day_of_week, $parameters);
+    }
+
+    /**
      * Cancels the provided schedule.
      *
      * @param String $schedule_id Id of the schedule to be canceled
@@ -258,8 +247,8 @@ class CronjobScheduler
         }
 
         // Find all schedules that are due to execute and which task is active
-        $temp = CronjobSchedule::findBySQL('active = 1 AND next_execution <= UNIX_TIMESTAMP() '
-                                          .'ORDER BY priority DESC, next_execution ASC');
+        $temp = CronjobSchedule::findBySQL('`active` = 1 AND `next_execution` <= UNIX_TIMESTAMP() '
+                                          .'ORDER BY `next_execution`');
         $schedules = array_filter($temp, function ($schedule) { return $schedule->task->active; });
 
         if (count($schedules) === 0) {
@@ -267,20 +256,19 @@ class CronjobScheduler
         }
 
         foreach ($schedules as $schedule) {
+            $log = new CronjobLog();
+            $log->schedule_id = $schedule->schedule_id;
+            $log->scheduled   = $schedule->next_execution;
+            $log->executed    = time();
+            $log->exception   = null;
+            $log->duration    = -1;
+
             try {
                 // Skip schedules with missing task classes
                 if (!$schedule->task->valid) {
                     throw new Exception(_('Die Klasse für den Cronjob-Task konnte nicht gefunden werden'));
                 }
 
-                $log = new CronjobLog();
-                $log->schedule_id = $schedule->schedule_id;
-                $log->scheduled   = $schedule->next_execution;
-                $log->executed    = time();
-                $log->exception   = null;
-                $log->duration    = -1;
-                $log->store();
-
                 // Start capturing output and measuring duration
                 ob_start();
                 $start_time = microtime(true);
@@ -297,6 +285,7 @@ class CronjobScheduler
                 $log->store();
             } catch (Exception $e) {
                 $log->exception = $e;
+                $log->store();
 
                 // Deactivate schedule
                 $schedule->deactivate();
diff --git a/lib/classes/DBManager.class.php b/lib/classes/DBManager.php
index 7854cff..7854cff 100644
--- a/lib/classes/DBManager.class.php
+++ b/lib/classes/DBManager.php
diff --git a/lib/classes/DIContainer.php b/lib/classes/DIContainer.php
index 9f0721b..c3d9b82 100644
--- a/lib/classes/DIContainer.php
+++ b/lib/classes/DIContainer.php
@@ -17,7 +17,7 @@ class DIContainer
     /**
      * Get the globally available instance of the container.
      *
-     * @return static
+     * @return ContainerInterface
      */
     public static function getInstance()
     {
@@ -47,9 +47,11 @@ class DIContainer
     {
         $builder = new ContainerBuilder();
         if (\Studip\ENV == 'production') {
-            $builder->enableCompilation($GLOBALS['TMP_PATH']);
+            $builder->enableCompilation(
+                self::getCompilationPath(),
+                self::getCompilationClass()
+            );
         }
-        $builder->ignorePhpDocErrors(true);
         $builder->addDefinitions('lib/bootstrap-definitions.php');
 
         $jsonapiSettings = require 'lib/classes/JsonApi/settings.php';
@@ -60,4 +62,14 @@ class DIContainer
 
         return $builder;
     }
+
+    public static function getCompilationPath(): string
+    {
+        return $GLOBALS['TMP_PATH'];
+    }
+
+    public static function getCompilationClass(): string
+    {
+        return 'CompiledContainer';
+    }
 }
diff --git a/lib/classes/DataFieldBoolEntry.class.php b/lib/classes/DataFieldBoolEntry.php
index da294b6..da294b6 100644
--- a/lib/classes/DataFieldBoolEntry.class.php
+++ b/lib/classes/DataFieldBoolEntry.php
diff --git a/lib/classes/DataFieldComboEntry.class.php b/lib/classes/DataFieldComboEntry.php
index 6047050..6047050 100644
--- a/lib/classes/DataFieldComboEntry.class.php
+++ b/lib/classes/DataFieldComboEntry.php
diff --git a/lib/classes/DataFieldDateEntry.class.php b/lib/classes/DataFieldDateEntry.php
index bf7d518..bf7d518 100644
--- a/lib/classes/DataFieldDateEntry.class.php
+++ b/lib/classes/DataFieldDateEntry.php
diff --git a/lib/classes/DataFieldEmailEntry.class.php b/lib/classes/DataFieldEmailEntry.php
index aafe7bb..aafe7bb 100644
--- a/lib/classes/DataFieldEmailEntry.class.php
+++ b/lib/classes/DataFieldEmailEntry.php
diff --git a/lib/classes/DataFieldEntry.class.php b/lib/classes/DataFieldEntry.php
index fd50a0b..eca0b4a 100644
--- a/lib/classes/DataFieldEntry.class.php
+++ b/lib/classes/DataFieldEntry.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * DataFieldEntry.class.php
+ * DataFieldEntry.php
  *
  * @author  Jan-Hendrik Willms <tleilax+studip@gmail.com>
  * @author  Marcus Lunzenauer <mlunzena@uos.de>
diff --git a/lib/classes/DataFieldLinkEntry.class.php b/lib/classes/DataFieldLinkEntry.php
index 702907f..702907f 100644
--- a/lib/classes/DataFieldLinkEntry.class.php
+++ b/lib/classes/DataFieldLinkEntry.php
diff --git a/lib/classes/DataFieldPhoneEntry.class.php b/lib/classes/DataFieldPhoneEntry.php
index d3a0e70..d3a0e70 100644
--- a/lib/classes/DataFieldPhoneEntry.class.php
+++ b/lib/classes/DataFieldPhoneEntry.php
diff --git a/lib/classes/DataFieldRadioEntry.class.php b/lib/classes/DataFieldRadioEntry.php
index 8699b69..8699b69 100644
--- a/lib/classes/DataFieldRadioEntry.class.php
+++ b/lib/classes/DataFieldRadioEntry.php
diff --git a/lib/classes/DataFieldSelectboxEntry.class.php b/lib/classes/DataFieldSelectboxEntry.php
index 8ac1a3c..8ac1a3c 100644
--- a/lib/classes/DataFieldSelectboxEntry.class.php
+++ b/lib/classes/DataFieldSelectboxEntry.php
diff --git a/lib/classes/DataFieldSelectboxMultipleEntry.class.php b/lib/classes/DataFieldSelectboxMultipleEntry.php
index 3abb373..3abb373 100644
--- a/lib/classes/DataFieldSelectboxMultipleEntry.class.php
+++ b/lib/classes/DataFieldSelectboxMultipleEntry.php
diff --git a/lib/classes/DataFieldTextareaEntry.class.php b/lib/classes/DataFieldTextareaEntry.php
index a48be98..a48be98 100644
--- a/lib/classes/DataFieldTextareaEntry.class.php
+++ b/lib/classes/DataFieldTextareaEntry.php
diff --git a/lib/classes/DataFieldTextareai18nEntry.class.php b/lib/classes/DataFieldTextareai18nEntry.php
index 9b6db40..9b6db40 100644
--- a/lib/classes/DataFieldTextareai18nEntry.class.php
+++ b/lib/classes/DataFieldTextareai18nEntry.php
diff --git a/lib/classes/DataFieldTextlineEntry.class.php b/lib/classes/DataFieldTextlineEntry.php
index 6062ed1..6062ed1 100644
--- a/lib/classes/DataFieldTextlineEntry.class.php
+++ b/lib/classes/DataFieldTextlineEntry.php
diff --git a/lib/classes/DataFieldTextlinei18nEntry.class.php b/lib/classes/DataFieldTextlinei18nEntry.php
index 9d1f344..9d1f344 100644
--- a/lib/classes/DataFieldTextlinei18nEntry.class.php
+++ b/lib/classes/DataFieldTextlinei18nEntry.php
diff --git a/lib/classes/DataFieldTextmarkupEntry.class.php b/lib/classes/DataFieldTextmarkupEntry.php
index 50115b9..50115b9 100644
--- a/lib/classes/DataFieldTextmarkupEntry.class.php
+++ b/lib/classes/DataFieldTextmarkupEntry.php
diff --git a/lib/classes/DataFieldTextmarkupi18nEntry.class.php b/lib/classes/DataFieldTextmarkupi18nEntry.php
index 0b3d7e6..0b3d7e6 100644
--- a/lib/classes/DataFieldTextmarkupi18nEntry.class.php
+++ b/lib/classes/DataFieldTextmarkupi18nEntry.php
diff --git a/lib/classes/DataFieldTimeEntry.class.php b/lib/classes/DataFieldTimeEntry.php
index 96e5835..96e5835 100644
--- a/lib/classes/DataFieldTimeEntry.class.php
+++ b/lib/classes/DataFieldTimeEntry.php
diff --git a/lib/classes/DatabaseObject.class.php b/lib/classes/DatabaseObject.php
index 2258adb..5c54229 100644
--- a/lib/classes/DatabaseObject.class.php
+++ b/lib/classes/DatabaseObject.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +--------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// DatabaseObject.class.php
+// DatabaseObject.php
 //
 // Class to provide basic properties of an DatabseObject in Stud.IP
 //
@@ -35,7 +35,7 @@ define("INSTANCEOF_DATABASEOBJECT", "DatabaseObject");
 
 
 /**
- * DatabaseObject.class.php
+ * DatabaseObject.php
  *
  * Class to provide basic properties of an DatabaseObject in Stud.IP
  *
diff --git a/lib/classes/DateFormatter.class.php b/lib/classes/DateFormatter.php
index 5f7c558..5309cbc 100644
--- a/lib/classes/DateFormatter.class.php
+++ b/lib/classes/DateFormatter.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /**
- * DateFormater.class.php - Handles the formatting of one date and associated rooms.
+ * DateFormater.php - Handles the formatting of one date and associated rooms.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
diff --git a/lib/classes/DbSnapshot.class.php b/lib/classes/DbSnapshot.php
index dfb4f89..33ea660 100644
--- a/lib/classes/DbSnapshot.class.php
+++ b/lib/classes/DbSnapshot.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// DbSnapshot.class.php
+// DbSnapshot.php
 // Class to provide snapshots of mysql result sets
 // Uses PHPLib DB Abstraction
 // Copyright (c) 2002 André Noack <andre.noack@gmx.net>
diff --git a/lib/classes/DbView.class.php b/lib/classes/DbView.php
index 81e9b91..0215f8e 100644
--- a/lib/classes/DbView.class.php
+++ b/lib/classes/DbView.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// DbView.class.php
+// DbView.php
 // Class to provide simple Views and Prepared Statements
 // Mainly for MySql, may work with other DBs (not tested)
 // Copyright (c) 2002 André Noack <andre.noack@gmx.net>
diff --git a/lib/classes/Debug/DebugBar.php b/lib/classes/Debug/DebugBar.php
new file mode 100644
index 0000000..bbd80c9
--- /dev/null
+++ b/lib/classes/Debug/DebugBar.php
@@ -0,0 +1,12 @@
+<?php
+namespace Studip\Debug;
+
+final class DebugBar
+{
+    public static function isActivated(): bool
+    {
+        return \Studip\ENV === 'development'
+            && ($_ENV['DEBUG_BAR'] ?? false)
+            && class_exists(\DebugBar\DebugBar::class);
+    }
+}
diff --git a/lib/classes/Debug/TraceableStudipPDO.php b/lib/classes/Debug/TraceableStudipPDO.php
new file mode 100644
index 0000000..6100c22
--- /dev/null
+++ b/lib/classes/Debug/TraceableStudipPDO.php
@@ -0,0 +1,24 @@
+<?php
+namespace Studip\Debug;
+
+use DebugBar\DataCollector\PDO\TraceablePDO;
+
+final class TraceableStudipPDO extends TraceablePDO
+{
+    /**
+     * Quotes a string for use in a query.
+     *
+     * @link   http://php.net/manual/en/pdo.quote.php
+     * @param  string $string The string to be quoted.
+     * @param  int    $parameter_type [optional] Provides a data type hint for drivers that have
+     * alternate quoting styles.
+     * @return string|bool A quoted string that is theoretically safe to pass into an SQL statement.
+     * Returns FALSE if the driver does not support quoting in this way.
+     */
+    #[\ReturnTypeWillChange]
+    public function quote($string, $parameter_type = null)
+    {
+        return $this->pdo->quote($string, $parameter_type);
+    }
+
+}
diff --git a/lib/classes/Debug/TrailsCollector.php b/lib/classes/Debug/TrailsCollector.php
new file mode 100644
index 0000000..f4b8a65
--- /dev/null
+++ b/lib/classes/Debug/TrailsCollector.php
@@ -0,0 +1,69 @@
+<?php
+namespace Studip\Debug;
+
+use DebugBar\DataCollector\DataCollector;
+use DebugBar\DataCollector\Renderable;
+use Trails\Controller;
+
+final class TrailsCollector extends DataCollector implements Renderable
+{
+    public function __construct(
+        private readonly Controller $controller
+    ) {
+        $this->useHtmlVarDumper(false);
+    }
+
+    public function collect()
+    {
+        $data = [];
+        foreach ($this->controller->get_assigned_variables() as $k => $v) {
+            if ($this->isHtmlVarDumperUsed()) {
+                $v = $this->getVarDumper()->renderVar($v);
+            } else if (!is_string($v)) {
+                $v = $this->getDataFormatter()->formatVar($v);
+            }
+            $data[$k] = $v;
+        }
+
+        ksort($data);
+
+        return $data;
+    }
+
+    public function getName()
+    {
+        return 'trails';
+    }
+
+    /**
+     * @return array
+     */
+    public function getAssets()
+    {
+        return $this->isHtmlVarDumperUsed() ? $this->getVarDumper()->getAssets() : [];
+    }
+
+    /**
+     * @return array[]
+     */
+    public function getWidgets()
+    {
+        $name = $this->getName();
+        $widget = $this->isHtmlVarDumperUsed()
+            ? 'PhpDebugBar.Widgets.HtmlVariableListWidget'
+            : 'PhpDebugBar.Widgets.VariableListWidget';
+
+        return [
+            $name => [
+                'icon'   => 'code',
+                'widget' => $widget,
+                'map' => $name,
+                'default' => '{}'
+            ],
+            "{$name}:badge" => [
+                'map' => "{$name}:variable__count",
+                'default' => count($this->controller->get_assigned_variables()),
+            ],
+        ];
+    }
+}
diff --git a/lib/classes/Event.interface.php b/lib/classes/Event.php
index 23f092b..23f092b 100644
--- a/lib/classes/Event.interface.php
+++ b/lib/classes/Event.php
diff --git a/lib/classes/EventLog.php b/lib/classes/EventLog.php
index 7336415..b20b997 100644
--- a/lib/classes/EventLog.php
+++ b/lib/classes/EventLog.php
@@ -87,7 +87,7 @@ class EventLog
         $offset = (int) $offset;
 
         $filter  = $this->sql_event_filter($action_id, $object_id, $parameters) ?: '1';
-        $filter .= " ORDER BY mkdate DESC, event_id DESC LIMIT {$offset}, 50";
+        $filter .= " ORDER BY event_id DESC LIMIT {$offset}, 50";
         $log_events = LogEvent::findBySQL($filter, $parameters);
         $events = [];
 
diff --git a/lib/classes/Feedback.class.php b/lib/classes/Feedback.php
index 26dbf55..26dbf55 100644
--- a/lib/classes/Feedback.class.php
+++ b/lib/classes/Feedback.php
diff --git a/lib/classes/FeedbackRange.interface.php b/lib/classes/FeedbackRange.php
index 863c197..863c197 100644
--- a/lib/classes/FeedbackRange.interface.php
+++ b/lib/classes/FeedbackRange.php
diff --git a/lib/classes/FileLock.class.php b/lib/classes/FileLock.php
index 064d41e..064d41e 100644
--- a/lib/classes/FileLock.class.php
+++ b/lib/classes/FileLock.php
diff --git a/lib/classes/ForumActivity.php b/lib/classes/ForumActivity.php
index bc00cf1..a6a685d 100644
--- a/lib/classes/ForumActivity.php
+++ b/lib/classes/ForumActivity.php
@@ -124,7 +124,7 @@ class ForumActivity
             'mkdate'       => $post['mkdate'] ?? time()
         ];
 
-        if ($post['anonymous']) {
+        if (!empty($post['anonymous'])) {
             $data['actor_type'] = 'anonymous';
             $data['actor_id']   = '';
         }
diff --git a/lib/classes/ForumEntry.php b/lib/classes/ForumEntry.php
index f98e59c..7ac5306 100644
--- a/lib/classes/ForumEntry.php
+++ b/lib/classes/ForumEntry.php
@@ -218,7 +218,7 @@ class ForumEntry  implements PrivacyObject
         array_pop($path);
         $data = array_pop($path);
 
-        return $data['id'] ?: false;
+        return $data['id'] ?? false;
     }
 
 
@@ -1029,7 +1029,7 @@ class ForumEntry  implements PrivacyObject
         $stmt = DBManager::get()->prepare("SELECT chdate FROM forum_entries
             WHERE lft > ? AND rgt < ? AND seminar_id = ?
             ORDER BY chdate DESC LIMIT 1");
-        $stmt->execute([$parent['lft'], $parent['rgt'], $parent['seminar_id']]);
+        $stmt->execute([$parent['lft'] ?? null, $parent['rgt'] ?? null, $parent['seminar_id'] ?? null]);
         $chdate = $stmt->fetchColumn();
 
         $stmt_insert = DBManager::get()->prepare("UPDATE forum_entries
diff --git a/lib/classes/ForumHelpers.php b/lib/classes/ForumHelpers.php
index 3054dbc..0c036cf 100644
--- a/lib/classes/ForumHelpers.php
+++ b/lib/classes/ForumHelpers.php
@@ -92,19 +92,15 @@ class ForumHelpers {
      */
     public static function translate_perm($perm)
     {
-        $mapping = [
+        return match ($perm) {
             'root'   => _('Root'),
             'admin'  => _('Administrator/-in'),
             'dozent' => _('Lehrende/-r'),
             'tutor'  => _('Tutor/-in'),
             'autor'  => _('Autor/-in'),
             'user'   => _('Leser/-in'),
-        ];
-
-        // TODO: Activate next when devboard reliably runs on PHP7
-        // return $mapping[$perm] ?? '';
-
-        return isset($mapping[$perm]) ? $mapping[$perm] : '';
+            default  => '',
+        };
     }
 
     /**
diff --git a/lib/classes/Fullcalendar.class.php b/lib/classes/Fullcalendar.php
index 467b583..db8364a 100644
--- a/lib/classes/Fullcalendar.class.php
+++ b/lib/classes/Fullcalendar.php
@@ -64,7 +64,7 @@ class Fullcalendar
 
     public function render()
     {
-        $factory = new \Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'] . '/templates');
+        $factory = new \Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'] . '/templates');
         $template = $factory->open('studip-fullcalendar.php');
         $real_data_name = sprintf('data-%s', $this->data_name);
         return $template->render(
diff --git a/lib/classes/I18N.php b/lib/classes/I18N.php
index d34ed0b..44252f3 100644
--- a/lib/classes/I18N.php
+++ b/lib/classes/I18N.php
@@ -61,10 +61,10 @@ class I18N
     /**
      * Protected constructor in order to always force a specific input type.
      *
-     * @param string|Flexi_Template $template   Template to use
+     * @param string|Flexi\Template $template   Template to use
      * @param string                $name       Name of the element
      * @param string|I18NString     $value      Value of the element
-     * @param array           $attributes Additional variables for the
+     * @param array                 $attributes Additional variables for the
      *                                          element
      */
     final protected function __construct($template, $name, $value, array $attributes)
diff --git a/lib/classes/I18NString.php b/lib/classes/I18NString.php
index 353062e..eab42ff 100644
--- a/lib/classes/I18NString.php
+++ b/lib/classes/I18NString.php
@@ -78,13 +78,8 @@ class I18NString implements JsonSerializable
 
     /**
      * Return the JSON representation of this i18n field in selected language.
-     *
-     * @return string
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function jsonSerialize()
+    public function jsonSerialize(): string
     {
         return (string) $this;
     }
@@ -184,7 +179,7 @@ class I18NString implements JsonSerializable
      */
     public function translation($lang)
     {
-        return $this->toArray()[$lang] ?? '';
+        return $this->toArray()[$lang] ?? null;
     }
 
     /**
diff --git a/lib/classes/Icon.class.php b/lib/classes/Icon.php
index ca0b9e0..6c586a0 100644
--- a/lib/classes/Icon.class.php
+++ b/lib/classes/Icon.php
@@ -338,7 +338,7 @@ class Icon
         $classNames = 'icon-role-' . $this->role;
 
         if (!self::isStatic($this->shape)) {
-            $classNames .= ' icon-shape-' . $this->shape;
+            $classNames .= ' icon-shape-' . $this->shapeToPath($this->shape);
         }
 
         $result['class'] = isset($result['class']) ? $result['class'] . ' ' . $classNames : $classNames;
@@ -385,8 +385,11 @@ class Icon
     // transforms a shape w/ possible additions (`shape`) to a path `(addition/)?shape`
     private function shapeToPath()
     {
-        return self::isStatic($this->shape)
-            ? $this->shape :
-            join('/', array_reverse(explode('+', preg_replace('/\.svg$/', '', $this->shape))));
+        if (self::isStatic($this->shape)) {
+            return $this->shape;
+        }
+        $shape = array_reverse(explode('/', $this->shape))[0];
+        $shape = explode('+', $shape)[0];
+        return $shape;
     }
 }
diff --git a/lib/classes/InstituteAvatar.class.php b/lib/classes/InstituteAvatar.php
index 8adbfba..8adbfba 100644
--- a/lib/classes/InstituteAvatar.class.php
+++ b/lib/classes/InstituteAvatar.php
diff --git a/lib/classes/InstituteCalendarHelper.class.php b/lib/classes/InstituteCalendarHelper.php
index 9412a34..6c934b4 100644
--- a/lib/classes/InstituteCalendarHelper.class.php
+++ b/lib/classes/InstituteCalendarHelper.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * InstituteCalendarHelper.class.php - class for institute calendar convenience functions
+ * InstituteCalendarHelper.php - class for institute calendar convenience functions
  *
  * @author      Timo Hartge <hartge@data-quest>
  * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
@@ -43,14 +43,6 @@ class InstituteCalendarHelper
      */
     public static function getResourceColumns($institut_id, $only_visible = false)
     {
-        /*
-        returns the columns in following format:
-            $columns = [
-                ['id' => '0', 'title' => 'Sammelspalte'],
-                ['id' => '1', 'title' => 'Spalte 1']
-            ];
-        */
-
         $columns = [];
         $inst_columns = [
             0 => ['Sammelspalte', 1]
@@ -206,13 +198,13 @@ class InstituteCalendarHelper
     /**
      * Looks up default color value for institute course events
      *
-     * @param Course $course
+     * @param SimpleORMap $context
      *
      * @return array course events with color value
      */
-    public static function getInstituteDefaultEventcolors($institut)
+    public static function getInstituteDefaultEventcolors($context)
     {
-        $df = DatafieldEntryModel::findByModel($institut, self::INST_DEFAULT_COLOR_DATAFIELD_ID);
+        $df = DatafieldEntryModel::findByModel($context, self::INST_DEFAULT_COLOR_DATAFIELD_ID);
         if ($df && $df[0]->content) {
             $event_colors = unserialize($df[0]->content);
         } else {
@@ -224,17 +216,17 @@ class InstituteCalendarHelper
     /**
      * Sets default institute course events color value for semtypes
      *
-     * @param Institut $institut
+     * @param SimpleORMap $context
      * @param string $semtype
      * @param string $color colorcode
      *
      * @return bool stored
      */
-    public static function setInstituteDefaultEventcolor($institut, $semtype, $color)
+    public static function setInstituteDefaultEventcolor($context, $semtype, $color)
     {
-        $df = DatafieldEntryModel::findByModel($institut, self::INST_DEFAULT_COLOR_DATAFIELD_ID);
+        $df = DatafieldEntryModel::findByModel($context, self::INST_DEFAULT_COLOR_DATAFIELD_ID);
         if ($df[0]) {
-            $event_colors = self::getInstituteDefaultEventcolors($institut);
+            $event_colors = self::getInstituteDefaultEventcolors($context);
             $event_colors[$semtype['name']] = $color;
             $df[0]->content = serialize($event_colors);
             return $df[0]->store();
@@ -317,7 +309,6 @@ class InstituteCalendarHelper
      */
     public static function getEvents($courses, $institut_id, $semester = null, $specific_weekday = null)
     {
-        $events = [];
         $today = date('w');
 
         $user_insts = array_map(function ($arr) {
@@ -330,9 +321,15 @@ class InstituteCalendarHelper
         $maxbigtime = (int) $max_time[0];
 
         $institut = Institute::find($institut_id);
+
+        if (!$institut) {
+            return [];
+        }
+
         $inst_default_colors = self::getInstituteDefaultEventcolors($institut);
 
-        Course::findAndMapMany(function ($course) use (
+        $events = [];
+        Course::findEachMany(function ($course) use (
             $courses,
             &$events,
             $today,
@@ -418,8 +415,8 @@ class InstituteCalendarHelper
                     }
                     if (!$backgroundcolor) {
                         $backgroundcolor = array_key_exists($semtype['name'], $inst_default_colors)
-                                         ? $inst_default_colors[$semtype['name']]
-                                         : self::DEFAULT_EVENT_COLOR;
+                            ? $inst_default_colors[$semtype['name']]
+                            : self::DEFAULT_EVENT_COLOR;
                     }
 
                     $textcolor = '#ffffff';
@@ -472,7 +469,7 @@ class InstituteCalendarHelper
      * @param SeminarCycleDate $cycle_date
      * @param string $institut_id
      *
-     * @return string enriched course info string for tooltip
+     * @return array enriched course info string for tooltip
      */
     public static function getCycleEvent($cycle_date, $institut_id)
     {
@@ -594,9 +591,8 @@ class InstituteCalendarHelper
      */
     private static function getCycleInfos($course, $cycle_date)
     {
-        $info_string = '';
 
-        $info_string .= $course->getFullName('number-name') . "\n";
+        $info_string = $course->getFullName('number-name') . "\n";
 
         $dozenten = [];
         foreach (CourseMember::findByCourseAndStatus($course->id, 'dozent') as $cmember) {
diff --git a/lib/classes/InstituteConfig.class.php b/lib/classes/InstituteConfig.php
index d1a51cb..551ea4d 100644
--- a/lib/classes/InstituteConfig.class.php
+++ b/lib/classes/InstituteConfig.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * InstituteConfig.class.php
+ * InstituteConfig.php
  * provides access to institute preferences
  *
  * @author  Jan-Hendrik Wullms <tleilax+studip@gmail.com>
diff --git a/lib/classes/Interactable.class.php b/lib/classes/Interactable.php
index 9796f91..9796f91 100644
--- a/lib/classes/Interactable.class.php
+++ b/lib/classes/Interactable.php
diff --git a/lib/classes/JSONArrayObject.class.php b/lib/classes/JSONArrayObject.php
index 896be3e..896be3e 100644
--- a/lib/classes/JSONArrayObject.class.php
+++ b/lib/classes/JSONArrayObject.php
diff --git a/lib/classes/JsonApi/JsonApiController.php b/lib/classes/JsonApi/JsonApiController.php
index 1718c52..614650d 100644
--- a/lib/classes/JsonApi/JsonApiController.php
+++ b/lib/classes/JsonApi/JsonApiController.php
@@ -375,12 +375,12 @@ class JsonApiController
      *
      * @param Request $request Request der eingehende Request
      *
-     * @return mixed entweder null oder das User-Objekt des
-     *               "eingeloggten" Nutzers
+     * @return null|\User entweder null oder das User-Objekt des "eingeloggten"
+     *                    Nutzers
      */
     public function getUser(Request $request)
     {
-        return $request->getAttribute(Authentication::USER_KEY, null);
+        return $request->getAttribute(Authentication::USER_KEY);
     }
 
     /**
diff --git a/lib/classes/JsonApi/Middlewares/Auth/OAuth1Strategy.php b/lib/classes/JsonApi/Middlewares/Auth/OAuth1Strategy.php
deleted file mode 100644
index 113ee09..0000000
--- a/lib/classes/JsonApi/Middlewares/Auth/OAuth1Strategy.php
+++ /dev/null
@@ -1,114 +0,0 @@
-<?php
-
-namespace JsonApi\Middlewares\Auth;
-
-use Psr\Http\Message\ResponseInterface as Response;
-use Psr\Http\Message\ServerRequestInterface as Request;
-
-class OAuth1Strategy implements Strategy
-{
-    /** @var callable */
-    protected $authenticator;
-
-    /** @var Request */
-    protected $request;
-
-    /** @var ?\User */
-    protected $user;
-
-    /**
-     * @param callable $authenticator
-     */
-    public function __construct(Request $request, $authenticator)
-    {
-        $this->request = $request;
-        $this->authenticator = $authenticator;
-
-        \OAuthStore::instance('PDO', ['conn' => \DBManager::get()]);
-    }
-
-    public function check()
-    {
-        return !is_null($this->user());
-    }
-
-    public function user()
-    {
-        if (!is_null($this->user)) {
-            return $this->user;
-        }
-
-        $this->user = $this->detect();
-
-        return $this->user;
-    }
-
-    public function addChallenge(Response $response)
-    {
-        return $response; //->withHeader('WWW-Authenticate', sprintf('Basic realm="%s"', 'Stud.IP JSON-API'));
-    }
-
-    private function detect(): ?\User
-    {
-        if (!\OAuthRequestVerifier::requestIsSigned()) {
-            return null;
-        }
-
-        $uri = (string) $this->request->getUri();
-        $method = $this->request->getMethod();
-
-        if ('GET' === strtoupper(($method))) {
-            $parameters = (array) $this->request->getQueryParams();
-        } elseif ('POST' === strtoupper(($method))) {
-            $parameters = (array) $this->request->getParsedBody();
-        } else {
-            $parameters = [];
-        }
-        $parameters = $this->getParamsFromAuthorizationHeader($this->request, $parameters);
-
-        $req = new \OAuthRequestVerifier($uri, $method, $parameters);
-
-        // Check oauth timestamp and deny access if timestamp is outdated
-        if ($req->getParam('oauth_timestamp') < strtotime('-6 hours')) {
-            return null;
-        }
-
-        $result = $req->verifyExtended('access');
-
-        $query = 'SELECT user_id FROM api_oauth_user_mapping WHERE oauth_id = ?';
-        $statement = \DBManager::get()->prepare($query);
-        $statement->execute([$result['user_id']]);
-
-        if (!$userId = $statement->fetchColumn()) {
-            return null;
-        }
-
-        /** @var \User */
-        return \User::find($userId);
-    }
-
-    private function getParamsFromAuthorizationHeader(Request $request, array $params): array
-    {
-        if ($request->hasHeader('Authorization')) {
-            $auth = $request->getHeaderLine('Authorization');
-            if (0 == strncasecmp($auth, 'OAuth', 4)) {
-                foreach (explode(',', substr($auth, 6)) as $v) {
-                    if (!strpos($v, '=')) {
-                        continue;
-                    }
-                    $v = trim($v);
-                    list($name, $value) = explode('=', $v, 2);
-                    if (!empty($value) && '"' == $value[0] && '"' == substr($value, -1)) {
-                        $value = substr(substr($value, 1), 0, -1);
-                    }
-
-                    if (0 != strcasecmp($name, 'realm')) {
-                        $params[$name] = $value;
-                    }
-                }
-            }
-        }
-
-        return $params;
-    }
-}
diff --git a/lib/classes/JsonApi/Middlewares/Authentication.php b/lib/classes/JsonApi/Middlewares/Authentication.php
index de92e15..bbcfef1 100644
--- a/lib/classes/JsonApi/Middlewares/Authentication.php
+++ b/lib/classes/JsonApi/Middlewares/Authentication.php
@@ -15,22 +15,21 @@ class Authentication
     // $user = $request->getAttribute(Authentication::USER_KEY);
     const USER_KEY = 'studip-user';
 
-    // a callable accepting two arguments username and password and
-    // returning either null or a Stud.IP user object
-    /** @var callable */
-    private $authenticator;
-
     /**
      * Der Konstruktor.
      *
-     * @param callable $authenticator ein Callable, das den Nutzernamen und
+     * @param \Closure $authenticator eine Closure, die den Nutzernamen und
      *                                das Passwort als Argumente erhält und
      *                                damit entweder einen Stud.IP-User-Objekt
      *                                oder null zurückgibt
+     * @param array    $excluded_strategies
      */
-    public function __construct($authenticator)
-    {
-        $this->authenticator = $authenticator;
+    public function __construct(
+        // a callable accepting two arguments username and password and
+        // returning either null or a Stud.IP user object
+        private readonly \Closure $authenticator,
+        private readonly array $excluded_strategies = []
+    ) {
     }
 
     /**
@@ -45,12 +44,7 @@ class Authentication
      */
     public function __invoke(Request $request, RequestHandler $handler)
     {
-        $guards = [
-            new Auth\SessionStrategy(),
-            new Auth\HttpBasicAuthStrategy($request, $this->authenticator),
-            new Auth\OAuth2Strategy($request, $this->authenticator),
-            new Auth\OAuth1Strategy($request, $this->authenticator),
-        ];
+        $guards = $this->getGuards($request);
 
         foreach ($guards as $guard) {
             if ($guard->check()) {
@@ -101,4 +95,24 @@ class Authentication
 
         return $request->withAttribute(self::USER_KEY, $user);
     }
+
+    /**
+     * @param Request $request
+     *
+     * @return array
+     */
+    protected function getGuards(Request $request): array
+    {
+        $guards = [
+            'session' => new Auth\SessionStrategy(),
+            'basic'   => new Auth\HttpBasicAuthStrategy($request, $this->authenticator),
+            'oauth2'  => new Auth\OAuth2Strategy($request, $this->authenticator),
+        ];
+
+        foreach ($this->excluded_strategies as $strategy) {
+            unset($guards[$strategy]);
+        }
+
+        return $guards;
+    }
 }
diff --git a/lib/classes/JsonApi/Middlewares/StudipMockNavigation.php b/lib/classes/JsonApi/Middlewares/StudipMockNavigation.php
index 34225d4..0883809 100644
--- a/lib/classes/JsonApi/Middlewares/StudipMockNavigation.php
+++ b/lib/classes/JsonApi/Middlewares/StudipMockNavigation.php
@@ -18,53 +18,38 @@ class DummyNavigation extends \Navigation implements \ArrayAccess
 
     /**
      * ArrayAccess: Check whether the given offset exists.
-     *
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return true;
     }
 
     /**
      * ArrayAccess: Get the value at the given offset.
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         return $this;
     }
 
     /**
      * ArrayAccess: Set the value at the given offset.
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[\ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
     }
 
     /**
      * ArrayAccess: Delete the value at the given offset.
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[\ReturnTypeWillChange]
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
     }
 
     /**
-     * IteratorAggregate: Create interator for request parameters.
-     *
-     * @todo Add \Traversable return type when Stud.IP requires PHP8 minimal
+     * IteratorAggregate: Create iterator for request parameters.
      */
-    #[\ReturnTypeWillChange]
-    public function getIterator()
+    public function getIterator(): \Traversable
     {
         return new \ArrayIterator();
     }
diff --git a/lib/classes/JsonApi/NonJsonApiController.php b/lib/classes/JsonApi/NonJsonApiController.php
index 8384b54..bfc51af 100644
--- a/lib/classes/JsonApi/NonJsonApiController.php
+++ b/lib/classes/JsonApi/NonJsonApiController.php
@@ -49,11 +49,11 @@ class NonJsonApiController
     }
 
     /**
-     * @return mixed
+     * @return null|\User
      */
     protected function getUser(Request $request)
     {
-        return $request->getAttribute(Authentication::USER_KEY, null);
+        return $request->getAttribute(Authentication::USER_KEY);
     }
 
     /**
diff --git a/lib/classes/JsonApi/RouteMap.php b/lib/classes/JsonApi/RouteMap.php
index 4f44165..63c69e6 100644
--- a/lib/classes/JsonApi/RouteMap.php
+++ b/lib/classes/JsonApi/RouteMap.php
@@ -5,8 +5,7 @@ namespace JsonApi;
 use JsonApi\Contracts\JsonApiPlugin;
 use JsonApi\Middlewares\Authentication;
 use JsonApi\Middlewares\DangerousRouteHandler;
-use JsonApi\Middlewares\JsonApi as JsonApiMiddleware;
-use JsonApi\Middlewares\StudipMockNavigation;
+use JsonApi\Routes\Consultations\SlotCreationCount;
 use JsonApi\Routes\Holidays\HolidaysShow;
 use Slim\Routing\RouteCollectorProxy;
 
@@ -49,7 +48,6 @@ use Slim\Routing\RouteCollectorProxy;
  *
  *   $this->app->post('/article/{id}/comments', MeineRoute::class);
  *
- * @see \JsonApi\Middlewares\JsonApi
  * @see \JsonApi\Middlewares\Authentication
  * @see \JsonApi\Contracts\JsonApiPlugin
  * @see http://www.slimframework.com/docs/objects/router.html#how-to-create-routes
@@ -118,11 +116,12 @@ class RouteMap
         $group->get('/status-groups/{id}', Routes\StatusgroupShow::class);
 
         $this->addAuthenticatedBlubberRoutes($group);
+        $this->addAuthenticatedClipboardRoutes($group);
         $this->addAuthenticatedConsultationRoutes($group);
         $this->addAuthenticatedContactsRoutes($group);
         $this->addAuthenticatedCoursesRoutes($group);
 
-        if (\PluginManager::getInstance()->getPlugin('CoursewareModule')) {
+        if (\PluginManager::getInstance()->getPlugin(\CoursewareModule::class)) {
             $this->addAuthenticatedCoursewareRoutes($group);
         }
 
@@ -155,7 +154,7 @@ class RouteMap
 
         $group->get('/studip/properties', Routes\Studip\PropertiesIndex::class);
 
-        if (\PluginManager::getInstance()->getPlugin('CoursewareModule')) {
+        if (\PluginManager::getInstance()->getPlugin(\CoursewareModule::class)) {
             $group->get('/public/courseware/{link_id}/courseware-structural-elements/{id}', Routes\Courseware\PublicStructuralElementsShow::class);
             $group->get('/public/courseware/{link_id}/courseware-structural-elements', Routes\Courseware\PublicStructuralElementsIndex::class);
         }
@@ -205,8 +204,26 @@ class RouteMap
         );
     }
 
+    private function addAuthenticatedClipboardRoutes(RouteCollectorProxy $group): void
+    {
+        $group->post('/clipboards', Routes\Clipboards\ClipboardsCreate::class);
+        $group->patch('/clipboards/{id}', Routes\Clipboards\ClipboardsUpdate::class);
+        $group->delete('/clipboards/{id}', Routes\Clipboards\ClipboardsDelete::class);
+
+        $group->get('/clipboard-items/{id}', Routes\Clipboards\ClipboardItemsShow::class);
+        $group->post('/clipboards/{id}/items', Routes\Clipboards\ClipboardItemsCreate::class);
+        $group->delete('/clipboards/{id}/items', Routes\Clipboards\ClipboardItemsDelete::class);
+        $group->delete('/clipboards/{id}/items/{itemId}', Routes\Clipboards\ClipboardItemsDelete::class);
+
+        $group->post('/clipboard-items', Routes\Clipboards\ClipboardItemsCreate::class);
+        $group->delete('/clipboard-items/{id}', Routes\Clipboards\ClipboardItemsDelete::class);
+    }
+
     private function addAuthenticatedConsultationRoutes(RouteCollectorProxy $group): void
     {
+        // TODO: I know, not very JSONAPI-like but it's a NonJsonApiController ¯\_(ツ)_/¯
+        $group->get('/consultation-slots/count', SlotCreationCount::class);
+
         $group->get('/{type:courses|institutes|users}/{id}/consultations', Routes\Consultations\BlocksByRangeIndex::class);
 
         $group->get('/consultation-blocks/{id}', Routes\Consultations\BlockShow::class);
diff --git a/lib/classes/JsonApi/Routes/Clipboards/Authority.php b/lib/classes/JsonApi/Routes/Clipboards/Authority.php
new file mode 100644
index 0000000..5cc053a
--- /dev/null
+++ b/lib/classes/JsonApi/Routes/Clipboards/Authority.php
@@ -0,0 +1,28 @@
+<?php
+namespace JsonApi\Routes\Clipboards;
+
+use User;
+
+final class Authority
+{
+    public static function canCreateClipboard(User $user): bool
+    {
+        return true;
+    }
+
+    public static function canAccessClipboard(User $user, \Clipboard $clipboard): bool
+    {
+        return $user->id === $clipboard->user_id
+            || $user->perms === 'root';
+    }
+
+    public static function canUpdateClipboard(User $user, \Clipboard $clipboard): bool
+    {
+        return self::canAccessClipboard($user, $clipboard);
+    }
+
+    public static function canDeleteClipboard(User $user, \Clipboard $clipboard): bool
+    {
+        return self::canUpdateClipboard($user, $clipboard);
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsCreate.php b/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsCreate.php
new file mode 100644
index 0000000..d57d0c5
--- /dev/null
+++ b/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsCreate.php
@@ -0,0 +1,106 @@
+<?php
+namespace JsonApi\Routes\Clipboards;
+
+use JsonApi\Errors\AuthorizationFailedException;
+use JsonApi\JsonApiController;
+use JsonApi\Routes\ValidationTrait;
+use JsonApi\Schemas\Clipboard;
+use Psr\Http\Message\{
+    ResponseInterface as Response,
+    ServerRequestInterface as Request
+};
+
+final class ClipboardItemsCreate extends JsonApiController
+{
+    use ValidationTrait;
+
+    public function __invoke(Request $request, Response $response, $args): Response
+    {
+        $json = $this->validate($request, $args);
+
+        $clipboard_id = $args['id'] ?? $json['data']['relationships']['clipboard']['data']['id'];
+        $clipboard = \Clipboard::find($clipboard_id);
+
+        $user = $this->getUser($request);
+        if (!Authority::canUpdateClipboard($user, $clipboard)) {
+            throw new AuthorizationFailedException();
+        }
+
+        $range_id   = $json['data']['attributes']['range_id'];
+        $range_type = $json['data']['attributes']['range_type'];
+
+        $item = \ClipboardItem::findOneBySql(
+            'clipboard_id = ? AND range_id = ? AND range_type = ?',
+            [$clipboard_id, $range_id, $range_type]
+        );
+
+        if ($item) {
+            return $this->getCodeResponse(302, [
+                'Location' => $this->getLinkToItem($item),
+            ]);
+        }
+
+        $item = \ClipboardItem::create([
+            'clipboard_id' => $clipboard_id,
+            'range_id'     => $range_id,
+            'range_type'   => $range_type,
+        ]);
+
+        return $this->getContentResponse($item);
+    }
+
+    protected function validateResourceDocument($json, $data)
+    {
+        $clipboardValidationError = $this->validateRequestContainsValidClipboard($json, $data);
+        if ($clipboardValidationError !== null) {
+            return $clipboardValidationError;
+        }
+
+        if (!self::arrayHas($json, 'data.attributes.range_id')) {
+            return 'No range_id defined';
+        }
+
+        if (!self::arrayHas($json, 'data.attributes.range_type')) {
+            return 'No range_type defined';
+        }
+
+        $range_type = self::arrayGet($json, 'data.attributes.range_type');
+        if (!is_a($range_type, \StudipItem::class, true)) {
+            return 'Range type must implement interface StudipItem';
+        }
+
+        return null;
+    }
+
+    private function validateRequestContainsValidClipboard($json, $data): ?string
+    {
+        if (isset($data['id'])) {
+            if (!\Clipboard::exists($data['id'])) {
+                return 'Provided clipboard id is invalid';
+            }
+        } else {
+            if (!self::arrayHas($json, 'data.relationships.clipboard')) {
+                return 'No clipboard relationship defined';
+            }
+
+            $clipboard = self::arrayGet($json, 'data.relationships.clipboard');
+            if (
+                !isset($clipboard['data']['type'], $clipboard['data']['id'])
+                || $clipboard['data']['type'] !== Clipboard::TYPE
+            ) {
+                return 'Defined clipboard relationship has invalid format.';
+            }
+            if (!\Clipboard::exists($clipboard['data']['id'])) {
+                return 'Related clipboard does not exist.';
+            }
+        }
+
+        return null;
+    }
+
+    private function getLinkToItem(\ClipboardItem $item): string
+    {
+        $json = $this->encoder->encodeData($item);
+        return json_decode($json, true)['data']['links']['self'];
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsDelete.php b/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsDelete.php
new file mode 100644
index 0000000..a9c7cd4
--- /dev/null
+++ b/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsDelete.php
@@ -0,0 +1,54 @@
+<?php
+namespace JsonApi\Routes\Clipboards;
+
+use JsonApi\Errors\BadRequestException;
+use JsonApi\Errors\RecordNotFoundException;
+use JsonApi\JsonApiController;
+use Psr\Http\Message\{
+    ResponseInterface as Response,
+    ServerRequestInterface as Request
+};
+
+final class ClipboardItemsDelete extends JsonApiController
+{
+    protected $allowedFilteringParameters = ['range_id'];
+
+    public function __invoke(Request $request, Response $response, $args): Response
+    {
+        $clipboard = \Clipboard::find($args['id']);
+        if (!$clipboard) {
+            throw new RecordNotFoundException('Clipboard not found');
+        }
+
+        $user = $this->getUser($request);
+        if (!Authority::canUpdateClipboard($user, $clipboard)) {
+            throw new \AccessDeniedException();
+        }
+
+        $item = null;
+        if (isset($args['itemId'])) {
+            $item = \ClipboardItem::find($args['itemId']);
+        } else {
+            $filtering = iterator_to_array($this->getQueryParameters()->getFilters());
+            if (!isset($filtering['range_id'])) {
+                throw new BadRequestException('No range_id filter given');
+            }
+            $item = \ClipboardItem::findOneBySQL(
+                'clipboard_id = ? AND range_id = ?',
+                [$clipboard->id, $filtering['range_id']]
+            );
+        }
+
+        if (!$item) {
+            throw new RecordNotFoundException('Item not found');
+        }
+
+        if ($item->clipboard_id !== $clipboard->id) {
+            throw new BadRequestException('Item does not belong to clipboard');
+        }
+
+        $item->delete();
+
+        return $this->getCodeResponse(204);
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsShow.php b/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsShow.php
new file mode 100644
index 0000000..3c91708
--- /dev/null
+++ b/lib/classes/JsonApi/Routes/Clipboards/ClipboardItemsShow.php
@@ -0,0 +1,28 @@
+<?php
+namespace JsonApi\Routes\Clipboards;
+
+use JsonApi\Errors\AuthorizationFailedException;
+use JsonApi\Errors\RecordNotFoundException;
+use JsonApi\JsonApiController;
+use Psr\Http\Message\{
+    ResponseInterface as Response,
+    ServerRequestInterface as Request
+};
+
+final class ClipboardItemsShow extends JsonApiController
+{
+    public function __invoke(Request $request, Response $response, $args): Response
+    {
+        $item = \ClipboardItem::find($args['id']);
+        if (!$item) {
+            throw new RecordNotFoundException();
+        }
+
+        $user = $this->getUser($request);
+        if (!Authority::canAccessClipboard($user, $item->clipboard)) {
+            throw new AuthorizationFailedException();
+        }
+
+        return $this->getContentResponse($item);
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Clipboards/ClipboardsCreate.php b/lib/classes/JsonApi/Routes/Clipboards/ClipboardsCreate.php
new file mode 100644
index 0000000..57fd9b9
--- /dev/null
+++ b/lib/classes/JsonApi/Routes/Clipboards/ClipboardsCreate.php
@@ -0,0 +1,46 @@
+<?php
+namespace JsonApi\Routes\Clipboards;
+
+use JsonApi\Errors\AuthorizationFailedException;
+use JsonApi\JsonApiController;
+use JsonApi\Routes\ValidationTrait;
+use Psr\Http\Message\{
+    ResponseInterface as Response,
+    ServerRequestInterface as Request
+};
+
+final class ClipboardsCreate extends JsonApiController
+{
+    use ValidationTrait;
+
+    public function __invoke(Request $request, Response $response, $args): Response
+    {
+        $user = $this->getUser($request);
+
+        if (!Authority::canCreateClipboard($user)) {
+            throw new AuthorizationFailedException();
+        }
+
+        $json = $this->validate($request, $args);
+
+        $clipboard = \Clipboard::create([
+            'name'    => $json['data']['attributes']['name'],
+            'user_id' => $user->id,
+        ]);
+
+        return $this->getContentResponse($clipboard);
+    }
+
+    protected function validateResourceDocument($json, $data)
+    {
+        if (!self::arrayHas($json, 'data.attributes.name')) {
+            return 'No name for the clipboard defined';
+        }
+
+        if (!trim(self::arrayGet($json, 'data.attributes.name'))) {
+            return 'Name of the clipboard may not be empty';
+        }
+
+        return null;
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Clipboards/ClipboardsDelete.php b/lib/classes/JsonApi/Routes/Clipboards/ClipboardsDelete.php
new file mode 100644
index 0000000..0897843
--- /dev/null
+++ b/lib/classes/JsonApi/Routes/Clipboards/ClipboardsDelete.php
@@ -0,0 +1,31 @@
+<?php
+namespace JsonApi\Routes\Clipboards;
+
+use JsonApi\Errors\AuthorizationFailedException;
+use JsonApi\Errors\RecordNotFoundException;
+use JsonApi\JsonApiController;
+use Psr\Http\Message\{
+    ResponseInterface as Response,
+    ServerRequestInterface as Request
+};
+
+final class ClipboardsDelete extends JsonApiController
+{
+    public function __invoke(Request $request, Response $response, $args): Response
+    {
+        $clipboard = \Clipboard::find($args['id']);
+        if (!$clipboard) {
+            throw new RecordNotFoundException();
+        }
+
+        $user = $this->getUser($request);
+
+        if (!Authority::canDeleteClipboard($user, $clipboard)) {
+            throw new AuthorizationFailedException();
+        }
+
+        $clipboard->delete();
+
+        return $this->getCodeResponse(204);
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Clipboards/ClipboardsUpdate.php b/lib/classes/JsonApi/Routes/Clipboards/ClipboardsUpdate.php
new file mode 100644
index 0000000..83d9539
--- /dev/null
+++ b/lib/classes/JsonApi/Routes/Clipboards/ClipboardsUpdate.php
@@ -0,0 +1,50 @@
+<?php
+namespace JsonApi\Routes\Clipboards;
+
+use JsonApi\Errors\AuthorizationFailedException;
+use JsonApi\Errors\RecordNotFoundException;
+use JsonApi\JsonApiController;
+use JsonApi\Routes\ValidationTrait;
+use Psr\Http\Message\{
+    ResponseInterface as Response,
+    ServerRequestInterface as Request
+};
+
+final class ClipboardsUpdate extends JsonApiController
+{
+    use ValidationTrait;
+
+    public function __invoke(Request $request, Response $response, $args): Response
+    {
+        $clipboard = \Clipboard::find($args['id']);
+        if (!$clipboard) {
+            throw new RecordNotFoundException();
+        }
+
+        $user = $this->getUser($request);
+
+        if (!Authority::canUpdateClipboard($user, $clipboard)) {
+            throw new AuthorizationFailedException();
+        }
+
+        $json = $this->validate($request, $args);
+
+        $clipboard->name = $json['data']['attributes']['name'];
+        $clipboard->store();
+
+        return $this->getContentResponse($clipboard);
+    }
+
+    protected function validateResourceDocument($json, $data)
+    {
+        if (!self::arrayHas($json, 'data.attributes.name')) {
+            return 'No name for the clipboard defined';
+        }
+
+        if (!trim(self::arrayGet($json, 'data.attributes.name'))) {
+            return 'Name of the clipboard may not be empty';
+        }
+
+        return null;
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Consultations/SlotCreationCount.php b/lib/classes/JsonApi/Routes/Consultations/SlotCreationCount.php
new file mode 100644
index 0000000..c378771
--- /dev/null
+++ b/lib/classes/JsonApi/Routes/Consultations/SlotCreationCount.php
@@ -0,0 +1,105 @@
+<?php
+namespace JsonApi\Routes\Consultations;
+
+use ConsultationBlock;
+use JsonApi\Errors\BadRequestException;
+use JsonApi\NonJsonApiController;
+use Neomerx\JsonApi\Exceptions\JsonApiException;
+use Neomerx\JsonApi\Schema\ErrorCollection;
+use Psr\Http\Message\ResponseInterface as Response;
+use Psr\Http\Message\ServerRequestInterface as Request;
+
+final class SlotCreationCount extends NonJsonApiController
+{
+    public function __invoke(Request $request, Response $response, array $args)
+    {
+        $parameters = $request->getQueryParams();
+
+        $this->validateParameters($parameters);
+
+        // Determine duration of a slot and pause times
+        $slot_count = ConsultationBlock::countSlots(
+            strtotime($parameters['start']),
+            strtotime($parameters['end']),
+            $parameters['dow'],
+            $parameters['interval'],
+            $parameters['duration'],
+            $parameters['pause_time'] ?? null,
+            $parameters['pause_duration'] ?? null
+        );
+
+        $response->getBody()->write((string) $slot_count);
+        return $response->withAddedHeader('Content-Type', 'application/json');
+    }
+
+    private function validateParameters(array $parameters): void
+    {
+        $collection = new ErrorCollection();
+
+        foreach (['start', 'end', 'dow', 'interval', 'duration'] as $key) {
+            if (!isset($parameters[$key])) {
+                $collection->addQueryParameterError($key, 'Parameter is missing');
+            }
+        }
+
+        if (isset($parameters['start'], $parameters['end'])) {
+            $start = strtotime($parameters['start']);
+            $end = strtotime($parameters['end']);
+
+            if (!$start) {
+                $collection->addQueryParameterError('start', 'Parameter has invalid datetime format');
+            }
+
+            if (!$end) {
+                $collection->addQueryParameterError('end', 'Parameter has invalid datetime format');
+            }
+
+            if ($start && $end && $start > $end) {
+                $collection->addQueryParameterError('start', 'Datetime value of start must be before end');
+            }
+        }
+
+        if (
+            isset($parameters['dow'])
+            && (
+                !ctype_digit($parameters['dow'])
+                || $parameters['dow'] < 0
+                || $parameters['dow'] > 6
+            )
+        ) {
+            $collection->addQueryParameterError('dow', 'Parameter must be a number between 0 and 6');
+        }
+
+        if (
+            isset($parameters['interval'])
+            && (
+                !ctype_digit($parameters['interval'])
+                || $parameters['interval'] < 0
+                || $parameters['interval'] > 4
+            )
+        ) {
+            $collection->addQueryParameterError('interval', 'Parameter must be a number between 0 and 4');
+        }
+
+        if (
+            isset($parameters['duration'])
+            && (
+                !ctype_digit($parameters['duration'])
+                || $parameters['duration'] <= 0
+            )
+        ) {
+            $collection->addQueryParameterError('duration', 'Parameter must be a positive number');
+        }
+
+        if (
+            isset($parameters['pause_time'], $parameters['duration'])
+            && $parameters['pause_time'] < $parameters['duration']
+        ) {
+            $collection->addQueryParameterError('pause_time', 'The defined time to a pause is shorter than the duration of a slot.');
+        }
+
+        if (count($collection) > 0) {
+            throw new JsonApiException($collection);
+        }
+    }
+}
diff --git a/lib/classes/JsonApi/Routes/Courseware/UnitsCreate.php b/lib/classes/JsonApi/Routes/Courseware/UnitsCreate.php
index e676507..d913966 100644
--- a/lib/classes/JsonApi/Routes/Courseware/UnitsCreate.php
+++ b/lib/classes/JsonApi/Routes/Courseware/UnitsCreate.php
@@ -100,6 +100,20 @@ class UnitsCreate extends JsonApiController
             'commentable' => 0
         ]);
 
+        \Courseware\Container::create([
+            'structural_element_id' => $struct->id,
+            'owner_id'              => $user->id,
+            'editor_id'             => $user->id,
+            'edit_blocker_id'       => '',
+            'position'              => 0,
+            'container_type'        => 'list',
+
+            'payload' => json_encode([
+                'colspan' => 'full',
+                'sections' => [['name' => _('erstes Element'), 'icon' => '','blocks' => []]]
+            ]),
+        ]);
+
         $unit = \Courseware\Unit::create([
             'range_id' => $range->getRangeId(),
             'range_type' => $range->getRangeType(),
diff --git a/lib/classes/JsonApi/Routes/Files/RangeFileRefsIndex.php b/lib/classes/JsonApi/Routes/Files/RangeFileRefsIndex.php
index 8f69d6a..773071e 100644
--- a/lib/classes/JsonApi/Routes/Files/RangeFileRefsIndex.php
+++ b/lib/classes/JsonApi/Routes/Files/RangeFileRefsIndex.php
@@ -13,7 +13,7 @@ class RangeFileRefsIndex extends AbstractRangeIndex
 
         $filerefs = [];
         foreach ($filesAndFolders['files'] as $file_object) {
-            if (method_exists($file_object, "getFileRef")) {
+            if (method_exists($file_object, 'getFileRef')) {
                 $filerefs[] = $file_object->getFileRef();
             }
         }
diff --git a/lib/classes/JsonApi/Routes/Files/SubfilerefsIndex.php b/lib/classes/JsonApi/Routes/Files/SubfilerefsIndex.php
index 0ff0603..2ed1a23 100644
--- a/lib/classes/JsonApi/Routes/Files/SubfilerefsIndex.php
+++ b/lib/classes/JsonApi/Routes/Files/SubfilerefsIndex.php
@@ -2,6 +2,7 @@
 
 namespace JsonApi\Routes\Files;
 
+use FileRef;
 use Psr\Http\Message\ServerRequestInterface as Request;
 use Psr\Http\Message\ResponseInterface as Response;
 use JsonApi\Errors\AuthorizationFailedException;
@@ -28,8 +29,14 @@ class SubfilerefsIndex extends JsonApiController
             throw new AuthorizationFailedException();
         }
 
-        $fileRefs = $folder->file_refs->getArrayCopy();
-        list($offset, $limit) = $this->getOffsetAndLimit();
+        $fileRefs = array_map(
+            function (\FileType $file): FileRef {
+                return $file->getFileRef();
+            },
+            $folder->getFiles()
+        );
+
+        [$offset, $limit] = $this->getOffsetAndLimit();
 
         return $this->getPaginatedContentResponse(
             array_slice($fileRefs, $offset, $limit),
diff --git a/lib/classes/JsonApi/Routes/Files/SubfoldersIndex.php b/lib/classes/JsonApi/Routes/Files/SubfoldersIndex.php
index e8f4d13..f0ad18c 100644
--- a/lib/classes/JsonApi/Routes/Files/SubfoldersIndex.php
+++ b/lib/classes/JsonApi/Routes/Files/SubfoldersIndex.php
@@ -19,20 +19,31 @@ class SubfoldersIndex extends JsonApiController
      */
     public function __invoke(Request $request, Response $response, $args)
     {
-        if (!$folder = \FileManager::getTypedFolder($args['id'])) {
+        $folder = \FileManager::getTypedFolder($args['id']);
+        if (!$folder) {
             throw new RecordNotFoundException();
         }
 
-        if (!Authority::canShowFolder($this->getUser($request), $folder)) {
+        $user = $this->getUser($request);
+
+        if (!Authority::canShowFolder($user, $folder)) {
             throw new AuthorizationFailedException();
         }
 
-        $subfolders = array_map(
-            function ($subfolder) {
-                return $subfolder->getTypedFolder();
+        $subfolders = array_reduce(
+            $folder->subfolders->getArrayCopy(),
+            function ($result, $subfolder) use ($user) {
+                $folder = $subfolder->getTypedFolder();
+
+                if (Authority::canShowFolder($user, $folder)) {
+                    $result[] = $folder;
+                }
+
+                return $result;
             },
-            $folder->subfolders->getArrayCopy()
+            []
         );
+
         list($offset, $limit) = $this->getOffsetAndLimit();
 
         return $this->getPaginatedContentResponse(
diff --git a/lib/classes/JsonApi/SchemaMap.php b/lib/classes/JsonApi/SchemaMap.php
index 97212bc..1498daf 100644
--- a/lib/classes/JsonApi/SchemaMap.php
+++ b/lib/classes/JsonApi/SchemaMap.php
@@ -2,6 +2,8 @@
 
 namespace JsonApi;
 
+use JsonApi\Schemas\Clipboard;
+
 /**
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
  */
@@ -19,6 +21,8 @@ class SchemaMap
             \BlubberThread::class => Schemas\BlubberThread::class,
 
             \CalendarDateAssignment::class => Schemas\CalendarDateAssignment::class,
+            \Clipboard::class => Schemas\Clipboard::class,
+            \ClipboardItem::class => Schemas\ClipboardItem::class,
             \ConsultationBlock::class => Schemas\ConsultationBlock::class,
             \ConsultationBooking::class => Schemas\ConsultationBooking::class,
             \ConsultationSlot::class => Schemas\ConsultationSlot::class,
diff --git a/lib/classes/JsonApi/Schemas/Clipboard.php b/lib/classes/JsonApi/Schemas/Clipboard.php
new file mode 100644
index 0000000..af90d73
--- /dev/null
+++ b/lib/classes/JsonApi/Schemas/Clipboard.php
@@ -0,0 +1,81 @@
+<?php
+namespace JsonApi\Schemas;
+
+use Neomerx\JsonApi\Contracts\Schema\ContextInterface;
+use Neomerx\JsonApi\Schema\Link;
+
+final class Clipboard extends SchemaProvider
+{
+    public const TYPE = 'clipboards';
+    public const REL_USER = 'user';
+    public const REL_ITEMS = 'clipboard-items';
+
+    /**
+     * @param \Clipboard $resource
+     */
+    public function getId($resource): ?string
+    {
+        return (string) $resource->id;
+    }
+
+    /**
+     * @param \Clipboard $resource
+     */
+    public function getAttributes($resource, ContextInterface $context): iterable
+    {
+        return [
+            'name'              => $resource->name,
+            'handler'           => $resource->handler,
+            'allows_item_class' => $resource->allowed_item_class,
+            'mkdate'            => date('c', $resource->mkdate),
+            'chdate'            => date('c', $resource->chdate),
+        ];
+    }
+
+    /**
+     * @param \Clipboard $resource
+     */
+    public function getRelationships($resource, ContextInterface $context): iterable
+    {
+        $relationships = [];
+
+        $isPrimary = $context->getPosition()->getLevel() === 0;
+        if ($isPrimary) {
+            $relationships = $this->getUserRelationship($relationships, $resource, $this->shouldInclude($context, self::REL_USER));
+            $relationships = $this->getItemsRelationship($relationships, $resource, $this->shouldInclude($context, self::REL_ITEMS));
+        }
+
+
+        return $relationships;
+    }
+
+    private function getUserRelationship(array $relationships, \Clipboard $clipboard, bool $includeData): array
+    {
+        $relationships[self::REL_USER] = [
+            self::RELATIONSHIP_LINKS => [
+                Link::RELATED => $this->createLinkToResource($clipboard->user),
+            ],
+            self::RELATIONSHIP_DATA => $includeData ? $clipboard->user : \User::build(['id' => $clipboard->user_id], false),
+        ];
+
+        return $relationships;
+    }
+
+    private function getItemsRelationship(array $relationships, \Clipboard $clipboard, bool $includeData): array
+    {
+        if ($includeData) {
+            $relatedItems = $clipboard->items;
+        } else {
+            $relatedItems = $clipboard->items->map(fn($item) => \ClipboardItem::build(['id' => $item->id], false));
+        }
+
+        $relationships[self::REL_ITEMS] = [
+            self::RELATIONSHIP_LINKS => [
+                Link::RELATED => $this->getRelationshipRelatedLink($clipboard, self::REL_ITEMS),
+            ],
+            self::RELATIONSHIP_DATA => $relatedItems,
+        ];
+
+        return $relationships;
+    }
+}
diff --git a/lib/classes/JsonApi/Schemas/ClipboardItem.php b/lib/classes/JsonApi/Schemas/ClipboardItem.php
new file mode 100644
index 0000000..9c84823
--- /dev/null
+++ b/lib/classes/JsonApi/Schemas/ClipboardItem.php
@@ -0,0 +1,61 @@
+<?php
+namespace JsonApi\Schemas;
+
+use Neomerx\JsonApi\Contracts\Schema\ContextInterface;
+use Neomerx\JsonApi\Schema\Link;
+
+final class ClipboardItem extends SchemaProvider
+{
+    public const TYPE = 'clipboard-items';
+    public const REL_CLIPBOARD = 'clipboard';
+
+    /**
+     * @param \ClipboardItem $resource
+     */
+    public function getId($resource): ?string
+    {
+        return (string) $resource->id;
+    }
+
+    /**
+     * @param \ClipboardItem $resource
+     */
+    public function getAttributes($resource, ContextInterface $context): iterable
+    {
+        return [
+            'range_id'   => $resource->range_id,
+            'range_type' => $resource->range_type,
+            'name'       => $resource->name,
+            'mkdate'     => date('c', $resource->mkdate),
+            'chdate'     => date('c', $resource->chdate),
+        ];
+    }
+
+    /**
+     * @param \ClipboardItem $resource
+     */
+    public function getRelationships($resource, ContextInterface $context): iterable
+    {
+        $relationships = [];
+
+        $isPrimary = $context->getPosition()->getLevel() === 0;
+        if ($isPrimary) {
+            $relationships = $this->getClipboardRelationship($relationships, $resource, $this->shouldInclude($context, self::REL_CLIPBOARD));
+        }
+
+
+        return $relationships;
+    }
+
+    private function getClipboardRelationship(array $relationships, \ClipboardItem $clipboardItem, bool $includeData): array
+    {
+        $relationships[self::REL_CLIPBOARD] = [
+            self::RELATIONSHIP_LINKS => [
+                Link::RELATED => $this->createLinkToResource($clipboardItem->clipboard),
+            ],
+            self::RELATIONSHIP_DATA => $includeData ? $clipboardItem->clipboard : \User::build(['id' => $clipboardItem->clipboard_id], false),
+        ];
+
+        return $relationships;
+    }
+}
diff --git a/lib/classes/JsonApi/Schemas/File.php b/lib/classes/JsonApi/Schemas/File.php
index 8eb8046..df0263a 100644
--- a/lib/classes/JsonApi/Schemas/File.php
+++ b/lib/classes/JsonApi/Schemas/File.php
@@ -29,7 +29,7 @@ class File extends SchemaProvider
             'chdate' => date('c', $resource['chdate']),
         ];
 
-        if ($resource['metadata']['url']) {
+        if (!empty($resource['metadata']['url'])) {
             if (FilesAuthority::canUpdateFile($this->currentUser, $resource)) {
                 $attributes['url'] = $resource['metadata']['url'];
             }
diff --git a/lib/classes/JsonApi/Schemas/Folder.php b/lib/classes/JsonApi/Schemas/Folder.php
index 2c61cae..4cb277e 100644
--- a/lib/classes/JsonApi/Schemas/Folder.php
+++ b/lib/classes/JsonApi/Schemas/Folder.php
@@ -169,14 +169,24 @@ class Folder extends SchemaProvider
         return $relationships;
     }
 
+    /**
+     * @param \FolderType $resource
+     */
     private function getFilesRelationship(array $relationships, $resource)
     {
+        $fileRefs = array_map(
+            function (\FileType $file): \FileRef {
+                return $file->getFileRef();
+            },
+            $resource->getFiles()
+        );
+
         $relationships[self::REL_FILE_REFS] = [
             self::RELATIONSHIP_LINKS => [
                 Link::RELATED => $this->getRelationshipRelatedLink($resource, self::REL_FILE_REFS),
             ],
             self::RELATIONSHIP_META => [
-                'count' => count($resource->file_refs)
+                'count' => count($fileRefs),
             ],
         ];
 
diff --git a/lib/classes/JsonApi/Schemas/WikiPage.php b/lib/classes/JsonApi/Schemas/WikiPage.php
index 857666e..f061ecc 100644
--- a/lib/classes/JsonApi/Schemas/WikiPage.php
+++ b/lib/classes/JsonApi/Schemas/WikiPage.php
@@ -152,7 +152,7 @@ class WikiPage extends SchemaProvider
      */
     private function addAuthorRelationship($relationships, $wiki, $includeList)
     {
-        if ($wiki->user_id) {
+        if ($wiki->user_id && $wiki->user_id !== 'nobody') {
             $relationships[self::REL_AUTHOR] = [
                 self::RELATIONSHIP_LINKS => [
                     Link::RELATED => $this->createLinkToResource($wiki->user),
diff --git a/lib/classes/LayoutMessage.interface.php b/lib/classes/LayoutMessage.php
index 7072788..7072788 100644
--- a/lib/classes/LayoutMessage.interface.php
+++ b/lib/classes/LayoutMessage.php
diff --git a/lib/classes/LinkButton.class.php b/lib/classes/LinkButton.php
index 40044b6..40044b6 100644
--- a/lib/classes/LinkButton.class.php
+++ b/lib/classes/LinkButton.php
diff --git a/lib/classes/LockRules.class.php b/lib/classes/LockRules.php
index 59679db..f1feb9f 100644
--- a/lib/classes/LockRules.class.php
+++ b/lib/classes/LockRules.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * LockRules.class.php
+ * LockRules.php
  *
  *
  * This program is free software; you can redistribute it and/or
@@ -16,7 +16,7 @@
 */
 
 /**
-* LockRules.class.php
+* LockRules.php
 *
 * This class contains only static methods dealing with lock rules
 *
diff --git a/lib/classes/Loggable.class.php b/lib/classes/Loggable.php
index ed0e162..ed0e162 100644
--- a/lib/classes/Loggable.class.php
+++ b/lib/classes/Loggable.php
diff --git a/lib/classes/LtiLink.php b/lib/classes/LtiLink.php
index 801b6c0..1423cef 100644
--- a/lib/classes/LtiLink.php
+++ b/lib/classes/LtiLink.php
@@ -310,12 +310,14 @@ class LtiLink
         // posted form data will always use CR LF
         $launch_params = preg_replace("/\r?\n/", "\r\n", $launch_params);
 
-        // In OAuth, request parameters must be sorted by name
-        ksort($launch_params);
-        $launch_params = http_build_query($launch_params, '', '&', PHP_QUERY_RFC3986);
-        $base_string = 'POST&' . rawurlencode($launch_url) . '&' . rawurlencode($launch_params);
-        $secret = rawurlencode($this->consumer_secret) . '&';
-
-        return base64_encode(hash_hmac($this->oauth_signature_method, $base_string, $secret, true));
+        return Studip\OAuth1::signRequest(
+            (new Slim\Psr7\Factory\ServerRequestFactory())->createServerRequest(
+                'POST',
+                $launch_url
+            )->withQueryParams($launch_params),
+            $this->consumer_secret,
+            '',
+            $this->oauth_signature_method
+        );
     }
 }
diff --git a/lib/classes/MVV.class.php b/lib/classes/MVV.php
index 67bbbeb..b4d9edf 100644
--- a/lib/classes/MVV.class.php
+++ b/lib/classes/MVV.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * MVV.class.php
+ * MVV.php
  * Helper class
  *
  * This program is free software; you can redistribute it and/or
@@ -843,7 +843,7 @@ class MVV implements Loggable {
     public static function getContentLanguageImagePath($language): string
     {
         $content_language = $GLOBALS['MVV_MODUL_DESKRIPTOR']['SPRACHE']['values'][$language]['content_language'];
-        return 'languages/' . ($GLOBALS['CONTENT_LANGUAGES'][$content_language]?$GLOBALS['CONTENT_LANGUAGES'][$content_language]['picture']:'lang_' . mb_strtolower($language) . '.gif');
+        return 'languages/' . ($GLOBALS['CONTENT_LANGUAGES'][$content_language]['picture'] ?? 'lang_' . mb_strtolower($language) . '.gif');
     }
 
 }
diff --git a/lib/classes/Markup.class.php b/lib/classes/Markup.php
index da040fa..dc6820f 100644
--- a/lib/classes/Markup.class.php
+++ b/lib/classes/Markup.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * Markup.class.php - Handling of Stud.IP- and HTML-markup.
+ * Markup.php - Handling of Stud.IP- and HTML-markup.
  **
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -363,7 +363,8 @@ class Markup
             'border-color',
             'border-style',
             'float',
-            'border'
+            'border',
+            'vertical-align'
         ]);
         $config->set('CSS.MaxImgLength', null);
 
diff --git a/lib/classes/MessageBox.class.php b/lib/classes/MessageBox.php
index 450851f..3573018 100644
--- a/lib/classes/MessageBox.class.php
+++ b/lib/classes/MessageBox.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /**
- * MessageBox.class.php
+ * MessageBox.php
  *
  * html boxes for different kinds of messages
  *
@@ -41,6 +41,7 @@ class MessageBox implements LayoutMessage
     public $details;
     public $close_details;
     protected $hide_close = false;
+    public static $counter = 0;
 
     /**
      * This function returns an exception message box. Use it only for system errors
@@ -141,18 +142,36 @@ class MessageBox implements LayoutMessage
     }
 
     /**
+     * Return whether this messagebox can be closed or not.
+     * @return bool
+     */
+    public function isCloseable(): bool
+    {
+        return $this->hide_close;
+    }
+
+    /**
      * This method renders a MessageBox object to a string.
      *
      * @return string   html output of the message box
      */
     public function __toString()
     {
+        $label = [
+            'exception' => _('Systemfehler'),
+            'error'     => _('Fehler'),
+            'warning'   => _('Warnung'),
+            'info'      => _('Hinweis'),
+            'success'   => _('Erfolg'),
+        ];
         return $GLOBALS['template_factory']->render('shared/message_box', [
             'class'         => $this->class,
             'message'       => $this->message,
             'details'       => is_array($this->details) ? $this->details : [],
             'close_details' => $this->close_details,
             'hide_close'    => $this->hide_close,
+            'label'         => $label[$this->class],
+            'counter'       => self::$counter++,
         ]);
     }
 }
diff --git a/lib/classes/Metrics.php b/lib/classes/Metrics.php
index c3874d5..e6a2925 100644
--- a/lib/classes/Metrics.php
+++ b/lib/classes/Metrics.php
@@ -191,7 +191,7 @@ class Metrics {
 
         // cache the activated MetricsPlugins
         if (!self::$metricPlugins) {
-            self::$metricPlugins = \PluginEngine::getPlugins('MetricsPlugin');
+            self::$metricPlugins = \PluginEngine::getPlugins(MetricsPlugin::class);
         }
 
         // call every MetricPlugin
diff --git a/lib/classes/ModulesNotification.class.php b/lib/classes/ModulesNotification.php
index 324b5c5..1dc361c 100644
--- a/lib/classes/ModulesNotification.class.php
+++ b/lib/classes/ModulesNotification.php
@@ -4,7 +4,7 @@
 # Lifter003: TEST
 # Lifter010: DONE - no html output in this file
 /**
-* ModulesNotification.class.php
+* ModulesNotification.php
 *
 * check for modules (global and local for institutes and Veranstaltungen), read and write
 *
@@ -17,7 +17,7 @@
 
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// Modules.class.php
+// Modules.php
 // Checks fuer Module (global und lokal fuer Veranstaltungen und Einrichtungen), Schreib-/Lesezugriff
 // Copyright (C) 2003 Cornelis Kater <ckater@gwdg.de>, Suchi & Berg GmbH <info@data-quest.de>
 // +---------------------------------------------------------------------------+
@@ -126,7 +126,8 @@ class ModulesNotification
             $navigation = MyRealmModel::getAdditionalNavigations($seminar_id, $s_data, null, $user_id, $visit_data[$seminar_id]);
             $n_data = [];
             foreach ($this->registered_notification_modules as $id => $m_data) {
-                if (in_array($id, $s_data['notification'])
+                if (
+                    in_array($id, $s_data['notification'])
                     && isset($navigation[$id])
                     && $navigation[$id]->getImage()
                     && $navigation[$id]->getImage()->getRole() === Icon::ROLE_ATTENTION
@@ -142,12 +143,15 @@ class ModulesNotification
             }
         }
         if (count($news)) {
-            $auth_plugin = User::find($user_id)->auth_plugin;
+            $user = User::find($user_id);
+            $auth_plugin = $user->auth_plugin;
             if (!is_a('StudipAuth' . ucfirst($auth_plugin), 'StudipAuthSSO', true)) {
                 $auth_plugin = null;
             }
             $template = $GLOBALS['template_factory']->open('mail/notification_html');
             $template->set_attribute('lang', getUserLanguagePath($user_id));
+            $template->set_attribute('rec_fullname', $user->getFullname('full'));
+            $template->set_attribute('rec_username', $user->username);
             $template->set_attribute('news', $news);
             $template->set_attribute('sso', $auth_plugin);
 
@@ -165,14 +169,14 @@ class ModulesNotification
         $base_url = URLHelper::setBaseURL('');
         URLHelper::setBaseURl($base_url);
         if ($nav instanceof Navigation && $nav->isVisible(true)) {
-                $url = 'seminar_main.php?again=yes&auswahl=' . $seminar_id . '&redirect_to=' . strtr($nav->getURL(), '?', '&');
-                $icon = $nav->getImage();
-                $text = $nav->getTitle();
-                if (!$text) {
-                    $text = $this->registered_notification_modules[$id]['name'];
-                }
-                $text .= ' - ' .  $nav->getLinkAttributes()['title'];
-                return compact('text', 'url', 'icon', 'seminar_id');
+            $url = 'seminar_main.php?again=yes&auswahl=' . $seminar_id . '&redirect_to=' . strtr($nav->getURL(), '?', '&');
+            $icon = $nav->getImage();
+            $text = $nav->getTitle();
+            if (!$text) {
+                $text = $this->registered_notification_modules[$id]['name'];
             }
+            $text .= ' - ' .  $nav->getLinkAttributes()['title'];
+            return compact('text', 'url', 'icon', 'seminar_id');
+        }
     }
 }
diff --git a/lib/classes/MultiDimArrayObject.class.php b/lib/classes/MultiDimArrayObject.php
index 459578f..b578018 100644
--- a/lib/classes/MultiDimArrayObject.class.php
+++ b/lib/classes/MultiDimArrayObject.php
@@ -78,13 +78,8 @@ class MultiDimArrayObject extends StudipArrayObject
 
     /**
      * Create a new iterator from an ArrayObject instance
-     *
-     * @return \Iterator
-     *
-     * @todo Add Traversable return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         $class = $this->iteratorClass;
 
@@ -96,12 +91,8 @@ class MultiDimArrayObject extends StudipArrayObject
      *
      * @param  mixed $key
      * @param  mixed $value
-     * @return void
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetSet($key, $value)
+    public function offsetSet($key, $value): void
     {
         $new_value = $this->recursiveArrayToArrayObjects($value);
         if (is_array($new_value)) {
diff --git a/lib/classes/MultiPersonSearch.class.php b/lib/classes/MultiPersonSearch.php
index 763ccd5..3ca617b 100644
--- a/lib/classes/MultiPersonSearch.class.php
+++ b/lib/classes/MultiPersonSearch.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * MultiPersonSearch.class.php
+ * MultiPersonSearch.php
  *
  * This class provides a GUI-element for searching, adding and removing
  * multiple persons. If JavaScript is enabled the GUI-element is shown
@@ -242,7 +242,7 @@ class MultiPersonSearch {
     /**
      * sets the search object.
      *
-     * @param SearchType object of type SearchType (e.g. SQLSearch.class.php)
+     * @param SearchType object of type SearchType (e.g. SQLSearch.php)
      *
      * @return MultiPersonSearch
      */
@@ -528,9 +528,9 @@ class MultiPersonSearch {
      * sets default values of the internal variables.
      */
     private function setDefaultValues() {
-        $this->title = _('Personen hinzufügen');
+        $this->title = '';
         $this->description = _('Bitte wählen Sie aus, wen Sie hinzufügen möchten.');
-        $this->linkIconPath = Icon::create("add", "clickable", ['title' => _('Personen hinzufügen')]);
+        $this->linkIconPath = Icon::create('add');
     }
 
     /**
diff --git a/lib/classes/MvvPerm.php b/lib/classes/MvvPerm.php
index 93f9f44..91e1e35 100644
--- a/lib/classes/MvvPerm.php
+++ b/lib/classes/MvvPerm.php
@@ -563,7 +563,7 @@ class MvvPerm {
     private static function getPrivileges($mvv_table)
     {
         if (self::$privileges === null) {
-            $cache = StudipCacheFactory::getCache();
+            $cache = \Studip\Cache\Factory::getCache();
             self::$privileges = unserialize($cache->read(MVV::CACHE_KEY . '/privileges'));
         }
 
@@ -576,7 +576,7 @@ class MvvPerm {
                     include $config_file; // Defines $privileges
                     self::$privileges[$mvv_table] = $privileges ?? [];
                 }
-                $cache = StudipCacheFactory::getCache();
+                $cache = \Studip\Cache\Factory::getCache();
                 $cache->write(MVV::CACHE_KEY . '/privileges', serialize(self::$privileges));
             }
         }
diff --git a/lib/classes/MvvQuickSearch.php b/lib/classes/MvvQuickSearch.php
index b0e79c0..b06de4f 100644
--- a/lib/classes/MvvQuickSearch.php
+++ b/lib/classes/MvvQuickSearch.php
@@ -1,6 +1,6 @@
 <?php
 
-require_once 'lib/classes/searchtypes/SQLSearch.class.php';
+require_once 'lib/classes/searchtypes/SQLSearch.php';
 
 class MvvQuickSearch extends SQLSearch
 {
diff --git a/lib/classes/MyRealmModel.php b/lib/classes/MyRealmModel.php
index 8008580..8997e78 100644
--- a/lib/classes/MyRealmModel.php
+++ b/lib/classes/MyRealmModel.php
@@ -93,35 +93,6 @@ class MyRealmModel
             }
         }
 
-        $sql = "SELECT COUNT(a.eval_id) as count,
-                       COUNT(IF((chdate > IFNULL(b.visitdate, :threshold) AND d.author_id !=:user_id ), a.eval_id, NULL)) AS neue,
-                       MAX(IF ((chdate > IFNULL(b.visitdate, :threshold) AND d.author_id != :user_id), chdate, 0)) AS last_modified
-                FROM eval_range a
-                INNER JOIN eval d
-                  ON (a.eval_id = d.eval_id AND d.startdate < UNIX_TIMESTAMP() AND (d.stopdate > UNIX_TIMESTAMP() OR d.startdate + d.timespan > UNIX_TIMESTAMP() OR (d.stopdate IS NULL AND d.timespan IS NULL)))
-                LEFT JOIN object_user_visits b
-                  ON (b.object_id = a.eval_id AND b.user_id = :user_id AND b.plugin_id = :plugin_id)
-                WHERE a.range_id = :course_id
-                GROUP BY a.range_id";
-
-        $statement = DBManager::get()->prepare($sql);
-        $statement->bindValue(':user_id', $user_id);
-        $statement->bindValue(':course_id', $object_id);
-        $statement->bindValue(':threshold', object_get_visit_threshold());
-        $statement->bindValue(':plugin_id', -2);
-        $statement->execute();
-        $result = $statement->fetch(PDO::FETCH_ASSOC);
-        if (!empty($result)) {
-            $count += $result['count'];
-            $neue += $result['neue'];
-            if (isset($my_obj['last_modified'], $result['last_modified']) && $result['last_modified']) {
-                if ($my_obj['last_modified'] < $result['last_modified']) {
-                    $my_obj['last_modified'] = $result['last_modified'];
-                }
-            }
-        }
-
-
         if ($neue || $count > 0) {
             $nav = new Navigation('vote', '#vote');
             if ($neue) {
@@ -163,16 +134,22 @@ class MyRealmModel
     public static function getCourses($min_sem_key, $max_sem_key, $params = [])
     {
         // init
-        $order_by          = $params['order_by'] ?? null;
-        $order             = $params['order'] ?? null;
-        $deputies_enabled  = $params['deputies_enabled'];
+        $order_by         = $params['order_by'] ?? null;
+        $order            = $params['order'] ?? null;
+        $deputies_enabled = $params['deputies_enabled'];
 
         $sem_data = Semester::getAllAsArray();
 
         $semester_ids = [];
         if (is_numeric($min_sem_key) && is_numeric($max_sem_key)) {
             foreach ($sem_data as $index => $data) {
-                if ($index >= $min_sem_key && $index <= $max_sem_key) {
+                if (
+                    $index >= $min_sem_key && $index <= $max_sem_key
+                    && (
+                        !isset($params['exactly'])
+                        || in_array($index, $params['exactly'])
+                    )
+                ) {
                     $semester_ids[] = $data['semester_id'] ?? '';
                 }
             }
@@ -232,7 +209,9 @@ class MyRealmModel
         $current_sem = null;
         foreach ($sem_data as $sem_key => $one_sem) {
             $current_sem = $sem_key;
-            if (!$one_sem['past']) break;
+            if (!$one_sem['past']) {
+                break;
+            }
         }
 
         if (isset($sem_data[$current_sem + 1])) {
@@ -242,7 +221,7 @@ class MyRealmModel
         }
 
         // Get the needed semester
-        if (!in_array($sem, ['', 'current', 'future', 'last', 'lastandnext'])) {
+        if (!in_array($sem, ['', 'current', 'future', 'last', 'lastandnext','lastbutone'])) {
             $semesters[] = Semester::getIndexById($sem);
         } else {
             switch ($sem) {
@@ -262,6 +241,10 @@ class MyRealmModel
                     $semesters[] = $current_sem;
                     $semesters[] = $max_sem;
                     break;
+                case 'lastbutone':
+                    $semesters[] = $current_sem - 2;
+                    $semesters[] = $current_sem;
+                    break;
                 default:
                     $semesters = array_keys($sem_data);
                     break;
@@ -281,11 +264,11 @@ class MyRealmModel
     public static function getPreparedCourses($sem = '', $params = [])
     {
         $semesters   = self::getSelectedSemesters($sem);
-        $current_semester_nr = Semester::getIndexById(@Semester::findCurrent()->id);
+        $current_semester_nr = Semester::getIndexById(Semester::findCurrent()->id ?? null);
         $min_sem_key = min($semesters);
         $max_sem_key = max($semesters);
         $group_field = $params['group_field'];
-        $courses     = self::getCourses($min_sem_key, $max_sem_key, $params);
+        $courses     = self::getCourses($min_sem_key, $max_sem_key, $params + ['exactly' => $semesters]);
         $show_semester_name = UserConfig::get($GLOBALS['user']->id)->SHOWSEM_ENABLE;
         $sem_courses = [];
 
@@ -332,7 +315,7 @@ class MyRealmModel
             $_course['visitdate']      = $visits[$course->id][0]['visitdate'];
             $_course['user_status']    = $user_status;
             $_course['gruppe']         = !$is_deputy ? $member_ships[$course->id]['gruppe'] ?? null : ($deputy ? $deputy->gruppe : null);
-            $_course['sem_number_end'] = $course->isOpenEnded() ? $max_sem_key : Semester::getIndexById($course->end_semester->id);
+            $_course['sem_number_end'] = $course->isOpenEnded() ? $max_sem_key : Semester::getIndexById($course->end_semester->id ?? null);
             $_course['sem_number']     = Semester::getIndexById($course->start_semester->id);
             $_course['tools']          = $course->tools;
             $_course['name']           = $course->name;
@@ -492,9 +475,9 @@ class MyRealmModel
     public static function setObjectVisits($object, $user_id, $timestamp = null)
     {
         // load plugins, so they have a chance to register themselves as observers
-        PluginEngine::getPlugins('StandardPlugin');
+        PluginEngine::getPlugins(StandardPlugin::class);
 
-        // Update news, votes and evaluations
+        // Update news and votes
         $query = "INSERT INTO object_user_visits
                     (object_id, user_id, plugin_id, visitdate, last_visitdate)
                   (
@@ -502,10 +485,6 @@ class MyRealmModel
                     FROM questionnaire_assignments
                     WHERE range_id = :id
                   ) UNION (
-                    SELECT eval_id, :user_id, '-2', :timestamp, 0
-                    FROM eval_range
-                    WHERE range_id = :id
-                  ) UNION (
                     SELECT `news_id`, :user_id, `pluginid`, :timestamp, 0
                     FROM `news_range`
                     JOIN `plugins` ON (`pluginclassname` = 'CoreOverview')
@@ -786,7 +765,7 @@ class MyRealmModel
         foreach ($sem_courses as $sem_key => $collection) {
             $_tmp_courses[$sem_key] = [];
             foreach ($collection as $course) {
-                $modules = Course::getMVVModulesForCourseId($course['seminar_id']);
+                $modules = Course::getMVVModulesForCourseId($course['seminar_id'], ['genehmigt']);
                 if ($modules) {
                     $modules = array_map(function (Modul $module) {
                         return $module->getDisplayName();
diff --git a/lib/classes/NotificationCenter.class.php b/lib/classes/NotificationCenter.php
index aaaa9e8..178fd62 100644
--- a/lib/classes/NotificationCenter.class.php
+++ b/lib/classes/NotificationCenter.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /*
- * NotificationCenter.class.php - NotificationCenter class
+ * NotificationCenter.php - NotificationCenter class
  *
  * Copyright (c) 2009  Elmar Ludwig
  *
diff --git a/lib/classes/OAuth1.php b/lib/classes/OAuth1.php
new file mode 100644
index 0000000..1695f9f
--- /dev/null
+++ b/lib/classes/OAuth1.php
@@ -0,0 +1,167 @@
+<?php
+namespace Studip;
+
+use Psr\Http\Message\ServerRequestInterface as Request;
+use RuntimeException;
+
+/**
+ * Basic oauth1 request handling for Stud.IP using PSR-7 http messages.
+ *
+ * @author Jan-Hendrik Willms <tleilax+studip@gmail.com>
+ * @license GPL2 or any later version
+ * @since Stud.IP 6.0
+ */
+final class OAuth1
+{
+    /**
+     * Signs a given request.
+     *
+     * @throws RuntimeException if a request for any other oauth version then
+     *                          1.0 shall be signed
+     */
+    public static function signRequest(
+        Request $request,
+        string  $consumerSecret,
+        string  $tokenSecret,
+        string  $method
+    ): string {
+        if (
+            isset($request->getQueryParams()['oauth_version'])
+            && $request->getQueryParams()['oauth_version'] !== '1.0'
+        ) {
+            throw new RuntimeException(self::class . ' only supports OAuth 1.0 requests');
+        }
+
+        return self::hash(
+            $method,
+            self::getSignatureBaseString($request),
+            self::urlencode($consumerSecret) . '&' . self::urlencode($tokenSecret)
+        );
+    }
+
+    /**
+     * Verifies an oauth request.
+     *
+     * @throws RuntimeException if any necessary oauth parameter is missing
+     */
+    public static function verifyRequest(
+        Request $request,
+        string  $consumerSecret,
+        string  $tokenSecret
+    ): bool {
+        $parameters = self::extractParameters($request);
+
+        $required = [
+            'oauth_consumer_key',
+            'oauth_nonce',
+            'oauth_signature',
+            'oauth_signature_method',
+            'oauth_timestamp',
+        ];
+
+        $missing = array_diff($required, array_keys($parameters));
+        if (count($missing) > 0) {
+            throw new RuntimeException('Missing oauth parameters ' . implode(', ', $missing));
+        }
+
+        $signatureToVerify = $parameters['oauth_signature'];
+        unset($parameters['oauth_signature']);
+
+        $signature = self::signRequest(
+            $request->withQueryParams($parameters),
+            $consumerSecret,
+            $tokenSecret,
+            $parameters['oauth_signature_method']
+        );
+
+        return $signature === $signatureToVerify;
+    }
+
+    /**
+     * Extracts the oauth parameters either from the Authorization header or
+     * from the query string.
+     */
+    public static function extractParameters(Request $request): array
+    {
+        $parameters = $request->getQueryParams();
+
+        $header = $request->getHeaderLine('Authorization');
+        if ($header && str_starts_with($header, 'OAuth ')) {
+            $temp = substr($header, 6);
+            $chunks = explode(',', $temp);
+
+            foreach ($chunks as $chunk) {
+                [$key, $value] = explode('=', $chunk, 2);
+                $value = trim($value, '"');
+                $parameters[$key] = self::urldecode($value);
+            }
+        }
+
+        return $parameters;
+    }
+
+    /**
+     * Creates the base string for the signature. It consists of:
+     *
+     * - The uppercase request method
+     * - The request URL
+     * - the sorted and urlencoded parameters of the request
+     *
+     * The urlencoded parts are concatenated together into a single string
+     * separated by the '&' character.
+     *
+     *
+     */
+    public static function getSignatureBaseString(Request $request): string
+    {
+        $parameters = $request->getQueryParams();
+        ksort($parameters);
+
+        return implode('&', array_map(
+            self::urlencode(...),
+            [
+                strtoupper($request->getMethod()),
+                (string) $request->getUri()->withQuery(''),
+                http_build_query($parameters, '', '&', PHP_QUERY_RFC3986),
+            ]
+        ));
+    }
+
+    /**
+     * Hashes a given text with a given key by the given method.
+     *
+     * @throws RuntimeException if the given hash method is not supported
+     */
+    public static function hash(string $method, string $text, string $key): string
+    {
+        $method = strtolower($method);
+        return match ($method) {
+            'hmac-sha1',   'sha1'   => base64_encode(hash_hmac('sha1', $text, $key, true)),
+            'hmac-sha256', 'sha256' => base64_encode(hash_hmac('sha256', $text, $key, true)),
+            'hmac-sha512', 'sha512' => base64_encode(hash_hmac('sha512', $text, $key, true)),
+
+            'plaintext' => $key,
+
+            default => throw new RuntimeException('Unsupported sigature method "' . $method . '"'),
+        };
+    }
+
+    /**
+     * Urlencodes a given input
+     */
+    public static function urldecode(string $input): string
+    {
+        return rawurldecode($input);
+    }
+
+    /**
+     * Urldecodes a given input
+     */
+    public static function urlencode(string $input): string
+    {
+        $encoded = rawurlencode($input);
+        return str_starts_with($encoded, '/%7E')
+            ? str_replace('/%7E', '/~', $encoded)
+            : $encoded;
+    }
+}
diff --git a/lib/classes/OAuth2/NegotiatesWithPsr7.php b/lib/classes/OAuth2/NegotiatesWithPsr7.php
index 0edf243..b2ee5a1 100644
--- a/lib/classes/OAuth2/NegotiatesWithPsr7.php
+++ b/lib/classes/OAuth2/NegotiatesWithPsr7.php
@@ -5,7 +5,7 @@ namespace Studip\OAuth2;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\ServerRequestInterface;
 use Slim\Psr7\Response;
-use Trails_Response;
+use Trails\Response as TrailsResponse;
 
 trait NegotiatesWithPsr7
 {
@@ -19,9 +19,9 @@ trait NegotiatesWithPsr7
         return new Response();
     }
 
-    protected function convertPsrResponse(ResponseInterface $response): Trails_Response
+    protected function convertPsrResponse(ResponseInterface $response): TrailsResponse
     {
-        $trailsResponse = new Trails_Response((string) $response->getBody(), [], $response->getStatusCode());
+        $trailsResponse = new TrailsResponse((string) $response->getBody(), [], $response->getStatusCode());
         foreach ($response->getHeaders() as $key => $values) {
             foreach ($values as $value) {
                 $trailsResponse->add_header($key, $value);
diff --git a/lib/classes/OpenGraph.php b/lib/classes/OpenGraph.php
index 75326aa..845f5cb 100644
--- a/lib/classes/OpenGraph.php
+++ b/lib/classes/OpenGraph.php
@@ -11,34 +11,71 @@ class OpenGraph
     /**
      * Extracts urls and their according open graph infos from a given string
      *
-     * @param String $string Text to extract urls and open graph infos from
+     * @param string|null $string Text to extract urls and open graph infos from
      * @return OpenGraphURLCollection containing the extracted urls
      */
-    public static function extract($string)
+    public static function extract(?string $string): OpenGraphURLCollection
     {
-        $collection = new OpenGraphURLCollection;
-
-        if (Config::get()->OPENGRAPH_ENABLE) {
-            $regexp = StudipCoreFormat::getStudipMarkup('links')['start'];
-            $matched = preg_match_all('/' . $regexp . '/ums', $string, $matches, PREG_SET_ORDER);
-            foreach ($matches as $match) {
-                $url = $match[2];
-
-                if (!$url) {
-                    continue;
-                }
-
-                if (!isLinkIntern($url)) {
-                    $og_url = OpenGraphURL::fromURL($url);
-                    if ($og_url && !$collection->find($og_url->id)) {
-                        $og_url->store();
-
-                        $collection[] = $og_url;
-                    }
-                }
+        $collection = new OpenGraphURLCollection();
+
+        if (!Config::get()->OPENGRAPH_ENABLE || !$string) {
+            return $collection;
+        }
+
+        if (Studip\Markup::isHtml($string)) {
+            $urls = self::extractUrlsFromHtml($string);
+        } else {
+            $urls = self::extractUrlsFromText($string);
+        }
+
+        foreach ($urls as $url) {
+            $og_url = OpenGraphURL::fromURL($url);
+            if ($og_url && !$collection->find($og_url->id)) {
+                $og_url->store();
+
+                $collection[] = $og_url;
             }
         }
 
         return $collection;
     }
+
+    public static function filterURLs(array $urls): array
+    {
+        return array_filter($urls, function (string $url): bool {
+            if (!$url) {
+                return false;
+            }
+
+            return !isLinkIntern($url);
+        });
+    }
+
+    public static function extractUrlsFromText(string $text): array
+    {
+        $regexp = StudipCoreFormat::getStudipMarkup('links')['start'];
+        preg_match_all('/' . $regexp . '/ums', $text, $matches, PREG_SET_ORDER);
+        $urls = array_column($matches, 2);
+
+        return self::filterURLs($urls);
+    }
+
+    public static function extractUrlsFromHtml(string $html): array
+    {
+        $document = new DOMDocument();
+        $document->loadHTML($html, LIBXML_NOWARNING | LIBXML_NOERROR);
+
+        $elements = $document->getElementsByTagName('a');
+
+        $urls = [];
+        foreach ($elements as $element) {
+            if (!$element->hasAttribute('href')) {
+                continue;
+            }
+
+            $urls[] = $element->getAttribute('href');
+        }
+
+        return self::filterURLs($urls);
+    }
 }
diff --git a/lib/classes/PageLayout.php b/lib/classes/PageLayout.php
index fca69b5..7f95b7a 100644
--- a/lib/classes/PageLayout.php
+++ b/lib/classes/PageLayout.php
@@ -36,6 +36,11 @@ class PageLayout
     private static $help_keyword;
 
     /**
+     * current help URL (or null if unset)
+     */
+    private static ?string $help_url = null;
+
+    /**
      * base item path for tab view (defaults to active item in top nav)
      */
     private static $tab_navigation_path = false;
@@ -134,6 +139,21 @@ class PageLayout
         self::addScript('studip-wysiwyg.js?v=' . $v);
 
         self::addStylesheet('print.css?v=' . $v, ['media' => 'print']);
+
+        if (Studip\Debug\DebugBar::isActivated()) {
+            $old_base = URLHelper::setBaseURL($GLOBALS['ABSOLUTE_URI_STUDIP']);
+
+            self::addHeadElement('link', [
+                'href' => URLHelper::getURL('dispatch.php/debugbar/css'),
+                'rel' => 'stylesheet',
+                'type' => 'text/css',
+            ]);
+            self::addHeadElement('script', [
+                'src' => URLHelper::getURL('dispatch.php/debugbar/js'),
+            ], '');
+
+            URLHelper::setBaseURL($old_base);
+        }
     }
 
     /**
@@ -179,7 +199,24 @@ class PageLayout
      */
     public static function getHelpKeyword()
     {
-        return isset(self::$help_keyword) ? self::$help_keyword : 'Basis.Allgemeines';
+        return self::$help_keyword ?? 'Basis.Allgemeines';
+    }
+
+    /**
+     * Set the help URL in the help bar. Pass null to fall back to the help keyword.
+     */
+    public static function setHelpUrl(?string $url): void
+    {
+        self::$help_url = $url;
+    }
+
+    /**
+     * Get the current help URL. If no URL is set explicitly, the URL for
+     * the help keyword is used.
+     */
+    public static function getHelpUrl(): ?string
+    {
+        return self::$help_url ?? format_help_url(self::getHelpKeyword());
     }
 
     /**
@@ -562,10 +599,18 @@ class PageLayout
         if (!isset($_SESSION['messages'])) {
             $_SESSION['messages'] = [];
         }
+
+        $structure = [
+            'type' => $message->class,
+            'message' => $message->message,
+            'details' => $message->details,
+            'closeable' => $message->isCloseable()
+        ];
+
         if ($id === null ) {
-            $_SESSION['messages'][] = $message;
+            $_SESSION['messages'][] = $structure;
         } else {
-            $_SESSION['messages'][$id] = $message;
+            $_SESSION['messages'][$id] = $structure;
         }
     }
 
diff --git a/lib/classes/PluginAdministration.php b/lib/classes/PluginAdministration.php
index 2732f58..faba3ec 100644
--- a/lib/classes/PluginAdministration.php
+++ b/lib/classes/PluginAdministration.php
@@ -440,27 +440,26 @@ class PluginAdministration
         // get plugin meta data
         $pluginclass = $manifest['pluginclassname'];
         $origin      = $manifest['origin'];
-        $min_version = $manifest['studipMinVersion'];
-        $max_version = $manifest['studipMaxVersion'];
+        $min_version = $manifest['studipMinVersion'] ?? null;
+        $max_version = $manifest['studipMaxVersion'] ?? null;
 
         // check for compatible version
-        if ((isset($min_version) && StudipVersion::olderThan($min_version)) ||
-            (isset($max_version) && StudipVersion::newerThan($max_version))) {
+        if (
+            (isset($min_version) && StudipVersion::olderThan($min_version))
+            || (isset($max_version) && StudipVersion::newerThan($max_version))
+        ) {
             throw new PluginInstallationException(_('Das Plugin ist mit dieser Stud.IP-Version nicht kompatibel.'));
         }
 
         // determine the plugin path
-        $basepath = Config::get()->PLUGINS_PATH;
         $pluginpath = $origin . '/' . $pluginclass;
 
-        $pluginregistered = $plugin_manager->getPluginInfo($pluginclass);
-
-        if ($pluginregistered) {
-            new PluginInstallationException(_('Das Plugin ist bereits registriert.'));
-        }
-
         // create database schema if needed
-        $this->createDBSchema($plugindir, $manifest, $pluginregistered);
+        $this->createDBSchema(
+            $plugindir,
+            $manifest,
+            (bool) $plugin_manager->getPluginInfo($pluginclass)
+        );
 
         // now register the plugin in the database
         $pluginid = $plugin_manager->registerPlugin($manifest['pluginname'], $pluginclass, $pluginpath);
diff --git a/lib/classes/PluginController.php b/lib/classes/PluginController.php
new file mode 100644
index 0000000..d57a90d
--- /dev/null
+++ b/lib/classes/PluginController.php
@@ -0,0 +1,72 @@
+<?php
+/**
+ * Copyright (c) 2014  Rasmus Fuhse <fuhse@data-quest.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+class PluginController extends StudipController
+{
+    public function __construct($dispatcher)
+    {
+        parent::__construct($dispatcher);
+
+        if (!isset($dispatcher->current_plugin)) {
+            throw new Exception('Plugin missing for plugin controller!');
+        }
+        $this->plugin = $dispatcher->current_plugin;
+
+        if ($this->plugin && $this->plugin->hasTranslation()) {
+            // Localization
+            $this->_ = function ($string) {
+                return call_user_func_array(
+                    [$this->plugin, '_'],
+                    func_get_args()
+                );
+            };
+
+            $this->_n = function ($string0, $tring1, $n) {
+                return call_user_func_array(
+                    [$this->plugin, '_n'],
+                    func_get_args()
+                );
+            };
+        }
+    }
+
+    /**
+     * Creates the body element id for this controller a given action.
+     *
+     * @param string $unconsumed_path Unconsumed path to extract action from
+     * @return string
+     */
+    protected function getBodyElementIdForControllerAndAction($unconsumed_path)
+    {
+        $body_id = implode('-', [
+            'plugin',
+            strtosnakecase(get_class($this->plugin)),
+            parent::getBodyElementIdForControllerAndAction($unconsumed_path),
+        ]);
+
+        return $body_id;
+    }
+
+    /**
+     * Intercepts all non-resolvable method calls in order to correctly handle
+     * calls to _ and _n.
+     *
+     * @param string $method
+     * @param array  $arguments
+     * @return mixed
+     */
+    public function __call($method, $arguments)
+    {
+        if (isset($this->_template_variables[$method]) && is_callable($this->_template_variables[$method])) {
+            return call_user_func_array($this->_template_variables[$method], $arguments);
+        }
+        return parent::__call($method, $arguments);
+    }
+}
diff --git a/lib/classes/Privacy.php b/lib/classes/Privacy.php
index 38e6e80..b38838c 100644
--- a/lib/classes/Privacy.php
+++ b/lib/classes/Privacy.php
@@ -59,7 +59,6 @@ class Privacy
             Courseware\UserProgress::class,
         ],
         'quest' => [
-            Evaluation::class,
             Questionnaire::class,
             QuestionnaireAnswer::class,
             QuestionnaireAnonymousAnswer::class,
@@ -115,7 +114,7 @@ class Privacy
         }
 
         if (!$section || $section === 'plugins') {
-            foreach (PluginEngine::getPlugins('PrivacyPlugin') as $plugin) {
+            foreach (PluginEngine::getPlugins(PrivacyPlugin::class) as $plugin) {
                 $plugin->exportUserData($storage);
             }
         }
diff --git a/lib/classes/PrivacyObject.interface.php b/lib/classes/PrivacyObject.php
index 8129634..8129634 100644
--- a/lib/classes/PrivacyObject.interface.php
+++ b/lib/classes/PrivacyObject.php
diff --git a/lib/classes/ProfileModel.php b/lib/classes/ProfileModel.php
deleted file mode 100644
index 6827ba6..0000000
--- a/lib/classes/ProfileModel.php
+++ /dev/null
@@ -1,213 +0,0 @@
-<?php
-/**
- * ProfileModel
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of
- * the License, or (at your option) any later version.
- *
- * @author      David Siegfried <david.siegfried@uni-oldenburg.de>
- * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
- * @category    Stud.IP
- * @since       2.4
- */
-
-class ProfileModel
-{
-    protected $perm;
-    /**
-     * Internal current selected user id
-     * @var String
-     */
-    protected $current_user;
-
-    /**
-     * Internal current logged in user id
-     * @var String
-     */
-    protected $user;
-
-    /**
-     * Internal user homepage visbilities
-     * @var array
-     */
-    protected $visibilities;
-
-    /**
-     * Get informations on depending selected user
-     * @param String $current_user
-     * @param String $user
-     */
-    public function __construct($current_user, $user)
-    {
-        $this->current_user = User::find($current_user);
-        $this->user         = User::find($user);
-        $this->visibilities = $this->getHomepageVisibilities();
-        $this->perm         = $GLOBALS['perm'];
-    }
-
-    /**
-     * Get the homepagevisibilities
-     *
-     * @return array
-     */
-    public function getHomepageVisibilities()
-    {
-        $visibilities = get_local_visibility_by_id(
-            $this->current_user ? $this->current_user->id : null,
-            'homepage'
-        );
-        if (is_array(json_decode($visibilities, true))) {
-            return json_decode($visibilities, true);
-        }
-        return [];
-    }
-
-    /**
-     * Returns the visibility value
-     *
-     * @return String
-     */
-    public function getVisibilityValue($param, $visibility = '')
-    {
-        if (Visibility::verify($visibility ?: $param, $this->current_user->user_id)) {
-            return $this->current_user->$param;
-        }
-        return false;
-    }
-
-    /**
-     * Returns a specific value of the visibilies
-     * @param String $param
-     * @return String
-     */
-
-    public function getSpecificVisibilityValue($param)
-    {
-        if (!empty($this->visibilities[$param])) {
-            return $this->visibilities[$param];
-        }
-        return false;
-    }
-
-    /**
-     * Creates an array with all seminars
-     *
-     * @return array
-     */
-    public function getDozentSeminars()
-    {
-        $courses = [];
-        $semester = [];
-        $next_semester = Semester::findNext();
-        $current_semester = Semester::findCurrent();
-        $previous_semester = Semester::findPrevious();
-        if ($next_semester) {
-            $semester[$next_semester->id] = $next_semester;
-        }
-        if ($current_semester) {
-            $semester[$current_semester->id] = $current_semester;
-        }
-        if ($previous_semester) {
-            $semester[$previous_semester->id] = $previous_semester;
-        }
-        $field = 'name';
-        if (Config::get()->IMPORTANT_SEMNUMBER) {
-            $field = "veranstaltungsnummer,{$field}";
-        }
-        $allcourses = new SimpleCollection(Course::findBySQL("INNER JOIN seminar_user USING(Seminar_id) WHERE user_id=? AND seminar_user.status='dozent' AND seminare.visible=1", [$this->current_user->id]));
-        foreach (array_filter($semester) as $one) {
-            $courses[(string) $one->name] = $allcourses->filter(function ($c) use ($one) {
-                if (Config::get()->HIDE_STUDYGROUPS_FROM_PROFILE && $c->isStudygroup()) {
-                    return false;
-                }
-                if (!$c->isOpenEnded()) {
-                    return $c->isInSemester($one);
-                } elseif ($one->isCurrent()) {
-                    return $c;
-                }
-                return false;
-            })->orderBy($field);
-
-            if (!$courses[(string) $one->name]->count()) {
-                unset($courses[(string) $one->name]);
-            }
-        }
-        return $courses;
-    }
-
-    /**
-     * Collect user datafield informations
-     *
-     * @return array
-     */
-    public function getDatafields()
-    {
-        // generische Datenfelder aufsammeln
-        $short_datafields = [];
-        $long_datafields  = [];
-        foreach (DataFieldEntry::getDataFieldEntries($this->current_user->user_id, 'user') as $entry) {
-            if ($entry->isVisible() && $entry->getDisplayValue()
-                && Visibility::verify($entry->getID(), $this->current_user->user_id))
-            {
-                if ($entry instanceof DataFieldTextareaEntry) {
-                    $long_datafields[] = $entry;
-                } else {
-                    $short_datafields[] = $entry;
-                }
-            }
-        }
-
-        return [
-            'long'  => $long_datafields,
-            'short' => $short_datafields,
-        ];
-    }
-
-    /**
-     * Filter long datafiels from the datafields
-     *
-     * @return array
-     */
-    public function getLongDatafields()
-    {
-        $datafields = $this->getDatafields();
-        $array      = [];
-
-        if (empty($datafields)) {
-            return null;
-        }
-        foreach ($datafields['long'] as $entry) {
-            $array[(string) $entry->getName()] = [
-                'content' => $entry->getDisplayValue(),
-                'visible' => '(' . $entry->getPermsDescription() . ')',
-            ];
-        }
-
-        return $array;
-    }
-
-    /**
-     * Filter short datafiels from the datafields
-     *
-     * @return array
-     */
-    public function getShortDatafields()
-    {
-        $shortDatafields = $this->getDatafields();
-        $array = [];
-
-        if (empty($shortDatafields)) {
-            return null;
-        }
-
-        foreach ($shortDatafields['short'] as $entry) {
-            $array[(string) $entry->getName()] = [
-                'content' => $entry->getDisplayValue(),
-                'visible' => '(' . $entry->getPermsDescription() . ')',
-            ];
-        }
-        return $array;
-    }
-}
diff --git a/lib/classes/QuestionType.interface.php b/lib/classes/QuestionType.php
index ada6005..03019fe 100644
--- a/lib/classes/QuestionType.interface.php
+++ b/lib/classes/QuestionType.php
@@ -60,7 +60,8 @@ interface QuestionType {
      *
      * Try to prefix all your input variables at least with the id of the question,
      * so that they will never conflict with other variables.
-     * @return Flexi_Template
+     *
+     * @return Flexi\Template
      */
     public function getDisplayTemplate();
 
@@ -82,11 +83,13 @@ interface QuestionType {
 
     /**
      * Returns a template with the results of this question.
+     *
      * @param $only_user_ids : array\null array of user_ids that the results should be restricted to.
      *                         this is used to show only a subset of results to the user for
      *                         visible evaluation of the results. If the questionnaire is anonymous
      *                         just do nothing.
-     * @return Flexi_Template
+     *
+     * @return Flexi\Template
      */
     public function getResultTemplate($only_user_ids = null);
 
diff --git a/lib/classes/QuickSearch.class.php b/lib/classes/QuickSearch.php
index d3983a3..f3e18cc 100644
--- a/lib/classes/QuickSearch.class.php
+++ b/lib/classes/QuickSearch.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /**
- * QuickSearch.class.php - GUI class for quciksearch
+ * QuickSearch.php - GUI class for quciksearch
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -66,7 +66,7 @@
  *  $searcher = new TeacherSearch();
  *  print QuickSearch::get("username", $searcher)->withButton->render();
  *  //code-end
- * Watch the SearchType class in lib/classes/searchtypes/SearchType.class.php
+ * Watch the SearchType class in lib/classes/searchtypes/SearchType.php
  * for details.
  * Enjoy!
  */
@@ -166,7 +166,7 @@ class QuickSearch
     /**
      * constructor which prepares a searchfield for persons, courses, institutes or
      * special items you may want to search for. This is a GUI-class, see
-     * QuickSearch.class.php for further documentation.
+     * QuickSearch.php for further documentation.
      *
      * @param string $name the name of the destinated variable in your html-form. Handle it
      * as if it was an '<input type="text" name="yourname">' input.
diff --git a/lib/classes/Range.interface.php b/lib/classes/Range.php
index 97aa074..97aa074 100644
--- a/lib/classes/Range.interface.php
+++ b/lib/classes/Range.php
diff --git a/lib/classes/RangeConfig.class.php b/lib/classes/RangeConfig.php
index b1030e3..ad48207 100644
--- a/lib/classes/RangeConfig.class.php
+++ b/lib/classes/RangeConfig.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * RangeConfig.class.php
+ * RangeConfig.php
  * provides access to object preferences
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/RangeTreeObject.class.php b/lib/classes/RangeTreeObject.php
index 579db43..06f84bf 100644
--- a/lib/classes/RangeTreeObject.class.php
+++ b/lib/classes/RangeTreeObject.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// RangeTreeObject.class.php
+// RangeTreeObject.php
 // Class to handle items in the "range tree"
 //
 // Copyright (c) 2002 André Noack <noack@data-quest.de>
diff --git a/lib/classes/RangeTreeObjectFak.class.php b/lib/classes/RangeTreeObjectFak.php
index 76cc366..9e980ca 100644
--- a/lib/classes/RangeTreeObjectFak.class.php
+++ b/lib/classes/RangeTreeObjectFak.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// RangeTreeObjectFak.class.php
+// RangeTreeObjectFak.php
 // Class to handle items in the "range tree"
 // 
 // Copyright (c) 2002 André Noack <noack@data-quest.de> 
diff --git a/lib/classes/RangeTreeObjectInst.class.php b/lib/classes/RangeTreeObjectInst.php
index c291dfc..d41b03d 100644
--- a/lib/classes/RangeTreeObjectInst.class.php
+++ b/lib/classes/RangeTreeObjectInst.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// RangeTreeObjectInst.class.php
+// RangeTreeObjectInst.php
 // Class to handle items in the "range tree"
 //
 // Copyright (c) 2002 André Noack <noack@data-quest.de>
diff --git a/lib/classes/Request.class.php b/lib/classes/Request.php
index 50ab8c4..d72a6a9 100644
--- a/lib/classes/Request.class.php
+++ b/lib/classes/Request.php
@@ -45,55 +45,40 @@ class Request implements ArrayAccess, IteratorAggregate
 
     /**
      * ArrayAccess: Check whether the given offset exists.
-     *
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return isset($this->params[$offset]);
     }
 
     /**
      * ArrayAccess: Get the value at the given offset.
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         return $this->params[$offset] ?? null;
     }
 
     /**
      * ArrayAccess: Set the value at the given offset.
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
         $this->params[$offset] = $value;
     }
 
     /**
      * ArrayAccess: Delete the value at the given offset.
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
         unset($this->params[$offset]);
     }
 
     /**
-     * IteratorAggregate: Create interator for request parameters.
-     *
-     * @todo Add Traversable return type when Stud.IP requires PHP8 minimal
+     * IteratorAggregate: Create iterator for request parameters.
      */
-    #[ReturnTypeWillChange]
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         return new ArrayIterator((array)$this->params);
     }
@@ -363,7 +348,7 @@ class Request implements ArrayAccess, IteratorAggregate
         //The second format and value is only added
         //when $second_param and $second_format are set
         //and a second value could be retrieved.
-        if ($second_param and $second_format) {
+        if ($second_param && $second_format) {
             $second_value = Request::get($second_param);
             if ($second_value) {
                 $combined_format .= ' ' . $second_format;
@@ -379,11 +364,22 @@ class Request implements ArrayAccess, IteratorAggregate
 
         //Now we return a DateTime object created from the
         //specified date value(s):
-        return DateTime::createFromFormat(
+        $result = DateTime::createFromFormat(
             $combined_format,
             $combined_value,
             $time_zone
         );
+
+        if (
+            $result
+            && !$second_param
+            && !$second_format
+            && !preg_match('/[aAghGHisvu]/', $format) // Ensure no time in format
+        ) {
+            $result->setTime(0, 0);
+        }
+
+        return $result;
     }
 
 
diff --git a/lib/classes/ResetButton.class.php b/lib/classes/ResetButton.php
index 8702c4b..8702c4b 100644
--- a/lib/classes/ResetButton.class.php
+++ b/lib/classes/ResetButton.php
diff --git a/lib/classes/ResponsiveHelper.php b/lib/classes/ResponsiveHelper.php
index 3e29db3..f02ee80 100644
--- a/lib/classes/ResponsiveHelper.php
+++ b/lib/classes/ResponsiveHelper.php
@@ -210,30 +210,29 @@ class ResponsiveHelper
             $courses = [];
         }
 
-        $items = [];
-
-        $standardIcon = Icon::create('seminar', Icon::ROLE_INFO_ALT)->asImagePath();
-
         // Add current course to list.
         if (Context::get()) {
             $courses[] = Context::get();
         }
 
-        foreach ($courses as $course) {
 
+        if (Context::isInstitute()) {
+            $avatarClass = InstituteAvatar::class;
+            $url = 'dispatch.php/institute/overview';
+            $standardIcon = Icon::create('institute', Icon::ROLE_INFO_ALT)->asImagePath();
+        } else {
             $avatarClass = CourseAvatar::class;
             $url = 'dispatch.php/course/details';
-            if (Context::isInstitute()) {
-                $avatarClass = InstituteAvatar::class;
-                $url = 'dispatch.php/institute/overview';
-                $standardIcon = Icon::create('institute', Icon::ROLE_INFO_ALT)->asImagePath();
-            }
+            $standardIcon = Icon::create('seminar', Icon::ROLE_INFO_ALT)->asImagePath();
+        }
 
+        $items = [];
+        foreach ($courses as $course) {
             $avatar = $avatarClass::getAvatar($course->id);
             $hasAvatar = $avatar->is_customized();
             $icon = $hasAvatar ? $avatar->getURL(Avatar::SMALL) : $standardIcon;
 
-            $cnav = [
+            $items['browse/my_courses/' . $course->id] = [
                 'icon'     => $icon,
                 'avatar'   => $hasAvatar,
                 'title'    => $course->getFullName(),
@@ -242,60 +241,60 @@ class ResponsiveHelper
                 'path'     => 'browse/my_courses/' . $course->id,
                 'visible'  => true,
                 'active'   => Context::getId() === $course->id,
-                'children' => []
+                'children' => self::getRangeNavigation(
+                    $course,
+                    'browse/my_courses/' . $course->id,
+                    $activated
+                ),
             ];
 
-            $path = 'browse/my_courses/' . $course->id;
-
-            foreach ($course->tools as $tool) {
-                if (Seminar_Perm::get()->have_studip_perm($tool->getVisibilityPermission(), $course->id)) {
-
-                    $studip_module = $tool->getStudipModule();
-                    if ($studip_module instanceof StudipModule) {
-                        $tool_nav = $studip_module->getTabNavigation($course->id) ?: [];
-                        foreach ($tool_nav as $nav_name => $navigation) {
-                            if ($nav_name && is_a($navigation, 'Navigation')) {
-                                if (!empty($tool->metadata['displayname'])) {
-                                    $navigation->setTitle($tool->getDisplayname());
-                                }
-                                $cnav['children'][$path . '/' . $nav_name] = [
-                                    'icon'     => $navigation->getImage() ? $navigation->getImage()->asImagePath() : '',
-                                    'title'    => $navigation->getTitle(),
-                                    'url'      => URLHelper::getURL($navigation->getURL(), ['cid' => $course->id]),
-                                    'parent'   => 'browse/my_courses/' . $course->id,
-                                    'path'     => 'browse/my_courses/' . $course->id . '/' . $nav_name,
-                                    'visible'  => true,
-                                    'active'   => $navigation->isActive(),
-                                    'children' => static::getChildren(
-                                        $navigation,
-                                        'browse/my_courses/' . $course->id . '/' . $nav_name,
-                                        $activated,
-                                        $course->id
-                                    ),
-                                ];
-                            }
-                        }
-                    }
-                }
-            }
+        }
 
-            if ($GLOBALS['perm']->have_studip_perm('tutor', $course->id)) {
-                $cnav['children'][$path . '/plus'] = [
-                    'icon' => Icon::create('add', Icon::ROLE_INFO_ALT)->asImagePath(),
-                    'title' => _('Mehr...'),
-                    'url' => URLHelper::getURL('dispatch.php/course/plus/index', ['cid' => $course->id]),
-                    'parent' => 'browse/my_courses/' . $course->id,
-                    'path' => 'browse/my_courses/' . $course->id . '/plus/index',
-                    'visible' => true,
-                    'active' => false,
-                    'children' => [],
-                ];
-            }
+        return $items;
+    }
+
+    private static function getRangeNavigation(Range $range, string $path_prefix, array &$activated): array
+    {
+        if ($range->id === Context::getId()) {
+            $navigation = Navigation::getItem('/course');
+        } else {
+            $navigation = new CourseNavigation($range);
+        }
 
-            $items['browse/my_courses/' . $course->id] = $cnav;
+        $result = [];
 
+        foreach ($navigation as $nav_name => $nav) {
+            $result[$path_prefix . '/' . $nav_name] = [
+                'icon'     => $nav->getImage() ? $nav->getImage()->asImagePath() : '',
+                'title'    => $nav->getTitle(),
+                'url'      => URLHelper::getURL($nav->getURL(), ['cid' => $range->id]),
+                'parent'   => 'browse/my_courses/' . $range->id,
+                'path'     => 'browse/my_courses/' . $range->id . '/' . $nav_name,
+                'visible'  => true,
+                'active'   => $nav->isActive(),
+                'children' => static::getChildren(
+                    $nav,
+                    'browse/my_courses/' . $range->id . '/' . $nav_name,
+                    $activated,
+                    $range->id
+                ),
+            ];
         }
 
-        return $items;
+        // Move admin page to the end
+        if (count($result) > 0) {
+            $first_path = array_keys($result)[0];
+            if (str_ends_with($first_path, '/admin')) {
+                $admin_navigation = array_slice(array_values($result), 0, 1)[0];
+                $admin_navigation['title'] = _('Verwaltung');
+                $admin_navigation['icon'] = Icon::create('add', Icon::ROLE_INFO_ALT)->asImagePath();
+                $result = array_merge(
+                    array_slice($result, 1),
+                    [$path_prefix . '/admin' => $admin_navigation]
+                );
+            }
+        }
+
+        return $result;
     }
 }
diff --git a/lib/classes/SQLQuery.php b/lib/classes/SQLQuery.php
index 0442604..6c8f49e 100644
--- a/lib/classes/SQLQuery.php
+++ b/lib/classes/SQLQuery.php
@@ -215,14 +215,22 @@ class SQLQuery
     /**
      * Fetches the whole resultset as an array of associative arrays. If you define
      * a sorm_class the result will be an array of the sorm-objects.
-     * @param $sorm_class_or_column : column name, a class of SimpleORMap or null for associative array.
-     * @return array of arrays or array of objects or array of values.
+     *
+     * @template T of SimpleORMap
+     * @param class-string<T>|string|null $sorm_class_or_column : column name, a class of SimpleORMap or null for associative array.
+     * @param int|null $max_results Maximum number of results to return
+     * @return array[]|T[]|mixed[] arrays or array of objects or array of values.
+     *
+     * @throws OverflowException if number of found rows is greater than $max_results
      */
-    public function fetchAll($sorm_class_or_column = null)
+    public function fetchAll($sorm_class_or_column = null, ?int $max_results = null)
     {
         NotificationCenter::postNotification('SQLQueryWillExecute', $this);
 
-        if (is_string($sorm_class_or_column) && !is_subclass_of($sorm_class_or_column, "SimpleORMap")) {
+        if (
+            is_string($sorm_class_or_column)
+            && !is_subclass_of($sorm_class_or_column, SimpleORMap::class)
+        ) {
             $sql = "SELECT `{$this->settings['table']}`.`{$sorm_class_or_column}` ";
         } else {
             $sql = "SELECT `{$this->settings['table']}`.* ";
@@ -239,16 +247,31 @@ class SQLQuery
 
         NotificationCenter::postNotification('SQLQueryDidExecute', $this);
 
-        if (is_string($sorm_class_or_column) && !is_subclass_of($sorm_class_or_column, "SimpleORMap")) {
-            return $statement->fetchAll(PDO::FETCH_COLUMN, 0);
+        if (
+            is_string($sorm_class_or_column)
+            && !is_subclass_of($sorm_class_or_column, SimpleORMap::class)
+        ) {
+            return $statement->fetchAll(PDO::FETCH_COLUMN);
         }
 
-        $alldata = $statement->fetchAll(PDO::FETCH_ASSOC);
-        if (!$sorm_class_or_column) {
-            return $alldata;
+        $statement->setFetchMode(PDO::FETCH_ASSOC);
+
+        $result = [];
+        $count = 0;
+        foreach ($statement as $row) {
+            $result[$count++] = $sorm_class_or_column ? $sorm_class_or_column::buildExisting($row) : $row;
+
+            if ($max_results && $count > $max_results) {
+                // Count remaining rows
+                $statement->setFetchMode(PDO::FETCH_COLUMN, 0);
+                while ($statement->fetch()) {
+                    $count += 1;
+                }
+                throw new OverflowException($count);
+            }
         }
 
-        return array_map("{$sorm_class_or_column}::buildExisting", $alldata);
+        return $result;
     }
 
     /**
diff --git a/lib/classes/Score.class.php b/lib/classes/Score.php
index 8f038f9..3b7f149 100644
--- a/lib/classes/Score.class.php
+++ b/lib/classes/Score.php
@@ -1,6 +1,6 @@
 <?
 /**
- * Score.class.php - Score class
+ * Score.php - Score class
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -121,7 +121,7 @@ class Score
     public static function GetMyScore($user_or_id = null)
     {
         $user = $user_or_id ? User::toObject($user_or_id) : User::findCurrent();
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         if ($cache->read("user_score_of_".$user->id)) {
             return $cache->read("user_score_of_".$user->id);
         }
@@ -212,7 +212,7 @@ class Score
             'date_column' => 'chdate'
         ];
 
-        foreach (PluginManager::getInstance()->getPlugins('ScorePlugin') as $plugin) {
+        foreach (PluginManager::getInstance()->getPlugins(ScorePlugin::class) as $plugin) {
             foreach ((array) $plugin->getPluginActivityTables() as $table) {
                 if ($table['table']) {
                     $tables[] = $table;
diff --git a/lib/classes/SemBrowse.class.php b/lib/classes/SemBrowse.php
index 7969a17..536b7e3 100644
--- a/lib/classes/SemBrowse.class.php
+++ b/lib/classes/SemBrowse.php
@@ -484,188 +484,6 @@ class SemBrowse {
         ob_end_flush();
     }
 
-    public function create_result_xls($headline = '')
-    {
-        require_once "vendor/write_excel/OLEwriter.php";
-        require_once "vendor/write_excel/BIFFwriter.php";
-        require_once "vendor/write_excel/Worksheet.php";
-        require_once "vendor/write_excel/Workbook.php";
-
-        global $SEM_TYPE, $SEM_CLASS, $TMP_PATH;
-
-        if (!$headline) {
-            $headline = _('Stud.IP Veranstaltungen') . ' - ' . Config::get()->UNI_NAME_CLEAN;
-        }
-        $tmpfile = null;
-        if (is_array($this->sem_browse_data['search_result'])
-                && count($this->sem_browse_data['search_result'])) {
-            if (!is_object($this->sem_tree)) {
-                $the_tree = TreeAbstract::GetInstance('StudipSemTree', false);
-            } else {
-                $the_tree = $this->sem_tree->tree;
-            }
-            list($group_by_data, $sem_data) = $this->get_result();
-            $tmpfile = $TMP_PATH . '/' . md5(uniqid('write_excel', 1));
-            // Creating a workbook
-            $workbook = new Workbook($tmpfile);
-            $head_format = $workbook->addformat();
-            $head_format->set_size(12);
-            $head_format->set_bold();
-            $head_format->set_align('left');
-            $head_format->set_align('vcenter');
-
-            $head_format_merged = $workbook->addformat();
-            $head_format_merged->set_size(12);
-            $head_format_merged->set_bold();
-            $head_format_merged->set_align('left');
-            $head_format_merged->set_align('vcenter');
-            $head_format_merged->set_merge();
-            $head_format_merged->set_text_wrap();
-
-            $caption_format = $workbook->addformat();
-            $caption_format->set_size(10);
-            $caption_format->set_align('left');
-            $caption_format->set_align('vcenter');
-            $caption_format->set_bold();
-
-            $data_format = $workbook->addformat();
-            $data_format->set_size(10);
-            $data_format->set_align('left');
-            $data_format->set_align('vcenter');
-
-            $caption_format_merged = $workbook->addformat();
-            $caption_format_merged->set_size(10);
-            $caption_format_merged->set_merge();
-            $caption_format_merged->set_align('left');
-            $caption_format_merged->set_align('vcenter');
-            $caption_format_merged->set_bold();
-
-
-            // Creating the first worksheet
-            $worksheet1 = $workbook->addworksheet(_('Veranstaltungen'));
-            $worksheet1->set_row(0, 20);
-            $worksheet1->write_string(0, 0, mb_convert_encoding($headline, 'WINDOWS-1252') ,$head_format);
-            $worksheet1->set_row(1, 20);
-            $worksheet1->write_string(
-                1,
-                0,
-                mb_convert_encoding(sprintf(
-                    _('%s Veranstaltungen gefunden %s, Gruppierung: %s'),
-                    count($sem_data),
-                    $this->sem_browse_data['sset'] ? '(' . _('Suchergebnis') . ')' : '',
-                    $this->group_by_fields[$this->sem_browse_data['group_by']]['name']
-                ), 'WINDOWS-1252'),
-                $caption_format
-            );
-
-            $worksheet1->write_blank(0, 1, $head_format);
-            $worksheet1->write_blank(0, 2, $head_format);
-            $worksheet1->write_blank(0, 3, $head_format);
-
-            $worksheet1->write_blank(1, 1, $head_format);
-            $worksheet1->write_blank(1, 2, $head_format);
-            $worksheet1->write_blank(1, 3, $head_format);
-
-            $worksheet1->set_column(0, 0, 70);
-            $worksheet1->set_column(0, 1, 25);
-            $worksheet1->set_column(0, 2, 25);
-            $worksheet1->set_column(0, 3, 50);
-
-            $row = 2;
-
-            foreach ($group_by_data as $group_field => $sem_ids) {
-                switch ($this->sem_browse_data['group_by']) {
-                    case 0:
-                        $headline = $this->search_obj->sem_dates[$group_field]['name'];
-                        break;
-                    case 1:
-                        if ($the_tree->tree_data[$group_field]) {
-                            $headline = $the_tree->getShortPath($group_field);
-                        } else {
-                            $headline =  _('keine Studienbereiche eingetragen');
-                        }
-                        break;
-                    case 3:
-                        $headline = $SEM_TYPE[$group_field]['name']
-                            ." ("
-                            . $SEM_CLASS[$SEM_TYPE[$group_field]['class']]['name'] . ')';
-                        break;
-                    default:
-                    $headline = $group_field;
-                }
-                ++$row;
-                $worksheet1->write_string($row, 0 , mb_convert_encoding($headline, 'WINDOWS-1252'), $caption_format);
-                $worksheet1->write_blank($row, 1, $caption_format);
-                $worksheet1->write_blank($row, 2, $caption_format);
-                $worksheet1->write_blank($row, 3, $caption_format);
-                ++$row;
-                if (is_array($sem_ids['Seminar_id'])) {
-                     foreach(array_keys($sem_ids['Seminar_id']) as $seminar_id){
-                        $seminar_obj = new Seminar($seminar_id);
-
-                        $sem_name = $seminar_obj->getName();
-                        $seminar_number = key($sem_data[$seminar_id]['VeranstaltungsNummer']);
-                        $sem_number_start = key($sem_data[$seminar_id]['sem_number']);
-                        $sem_number_end = key($sem_data[$seminar_id]['sem_number_end']);
-                        if ($sem_number_start != $sem_number_end) {
-                            $sem_name .= ' (' . $this->search_obj->sem_dates[$sem_number_start]['name'] . ' - ';
-                            $sem_name .= ($sem_number_end == -1 ? _('unbegrenzt') : $this->search_obj->sem_dates[$sem_number_end]['name']) . ')';
-                        } elseif ($this->sem_browse_data['group_by']) {
-                            $sem_name .= ' (' . $this->search_obj->sem_dates[$sem_number_start]['name'] . ')';
-                        }
-                        // is this sem a studygroup?
-                        $studygroup_mode = SeminarCategories::GetByTypeId($seminar_obj->getStatus())->studygroup_mode;
-                        if ($studygroup_mode) {
-                            $sem_name = $seminar_obj->getName() . ' (' . _('Studiengruppe');
-                            if ($seminar_obj->admission_prelim) $sem_name .= ', '. _('Zutritt auf Anfrage');
-                            $sem_name .= ')';
-                        }
-                        $worksheet1->write_string($row, 0, mb_convert_encoding($sem_name, 'WINDOWS-1252'), $data_format);
-                        //create Turnus field
-                        $temp_turnus_string = $seminar_obj->getFormattedTurnus(true);
-                        //Shorten, if string too long (add link for details.php)
-                        if (mb_strlen($temp_turnus_string) > 245) {
-                            $temp_turnus_string = mb_substr($temp_turnus_string,
-                                    0, mb_strpos(
-                                            mb_substr($temp_turnus_string, 245,
-                                                mb_strlen($temp_turnus_string)
-                                            ), ','
-                                        ) + 246);
-                            $temp_turnus_string .= ' ... (' . _('mehr') . ')';
-                        }
-                        $worksheet1->write_string($row, 1, mb_convert_encoding($seminar_number, 'WINDOWS-1252'), $data_format);
-                        $worksheet1->write_string($row, 2, mb_convert_encoding($temp_turnus_string, 'WINDOWS-1252'), $data_format);
-
-                        $doz_name = [];
-                        $c = 0;
-                        reset($sem_data[$seminar_id]['fullname']);
-                        foreach ($sem_data[$seminar_id]['username'] as $anzahl1) {
-                            if ($c == 0) {
-                                $d_name = key($sem_data[$seminar_id]['fullname']);
-                                $anzahl2 = current($sem_data[$seminar_id]['fullname']);
-                                next($sem_data[$seminar_id]['fullname']);
-                                $c = $anzahl2 / $anzahl1;
-                                $doz_name = array_merge($doz_name, array_fill(0, $c, $d_name));
-                            }
-                            --$c;
-                        }
-                        $doz_position = array_keys($sem_data[$seminar_id]['position']);
-                        if (is_array($doz_name)){
-                            if (count($doz_position) != count($doz_name)) {
-                                $doz_position = range(1, count($doz_name));
-                            }
-                            array_multisort($doz_position, $doz_name);
-                            $worksheet1->write_string($row, 3, mb_convert_encoding(join(', ', $doz_name), 'WINDOWS-1252'), $data_format);
-                        }
-                        ++$row;
-                    }
-                }
-            }
-            $workbook->close();
-        }
-        return $tmpfile;
-    }
-
     public function get_result()
     {
         global $_fullname_sql, $user;
diff --git a/lib/classes/SemClass.class.php b/lib/classes/SemClass.php
index 09580e2..2a038e2 100644
--- a/lib/classes/SemClass.class.php
+++ b/lib/classes/SemClass.php
@@ -304,9 +304,11 @@ class SemClass implements ArrayAccess
     public function isModuleAllowed($modulename)
     {
         return !$this->isModuleForbidden($modulename)
-            && (empty($this->data['modules'][$modulename])
-            || !$this->data['modules'][$modulename]['sticky']
-            || $this->data['modules'][$modulename]['activated']);
+            && (
+                empty($this->data['modules'][$modulename])
+                || empty($this->data['modules'][$modulename]['sticky'])
+                || !empty($this->data['modules'][$modulename]['activated'])
+            );
     }
 
     /**
@@ -317,8 +319,8 @@ class SemClass implements ArrayAccess
     public function isModuleMandatory($module)
     {
         return isset($this->data['modules'][$module])
-            && $this->data['modules'][$module]['sticky']
-            && $this->data['modules'][$module]['activated'];
+            && !empty($this->data['modules'][$module]['sticky'])
+            && !empty($this->data['modules'][$module]['activated']);
     }
 
     public function getSemTypes()
@@ -387,7 +389,7 @@ class SemClass implements ArrayAccess
                 "chdate = UNIX_TIMESTAMP() " .
             "WHERE id = :id ".
         "");
-        StudipCacheFactory::getCache()->expire('DB_SEM_CLASSES_ARRAY');
+        \Studip\Cache\Factory::getCache()->expire('DB_SEM_CLASSES_ARRAY');
         return $statement->execute([
             'id' => $this->data['id'],
             'name' => $this->data['name'],
@@ -451,7 +453,7 @@ class SemClass implements ArrayAccess
                 DELETE FROM sem_classes
                 WHERE id = :id
             ");
-            StudipCacheFactory::getCache()->expire('DB_SEM_CLASSES_ARRAY');
+            \Studip\Cache\Factory::getCache()->expire('DB_SEM_CLASSES_ARRAY');
             return $statement->execute([
                 'id' => $this->data['id']
             ]);
@@ -478,11 +480,8 @@ class SemClass implements ArrayAccess
      * deprecated, does nothing, should not be used
      * @param string $offset
      * @param mixed $value
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
     }
 
@@ -490,12 +489,8 @@ class SemClass implements ArrayAccess
      * Compatibility function with old $SEM_CLASS variable for plugins. Maps the
      * new array-structure to the old boolean values.
      * @param integer $offset: name of attribute
-     * @return boolean|(localized)string
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         switch ($offset) {
             case "name":
@@ -528,12 +523,8 @@ class SemClass implements ArrayAccess
     /**
      * ArrayAccess method to check if an attribute exists.
      * @param int $offset
-     * @return bool
-     *
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return isset($this->data[$offset]);
     }
@@ -541,11 +532,8 @@ class SemClass implements ArrayAccess
     /**
      * deprecated, does nothing, should not be used
      * @param string $offset
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
     }
 
@@ -564,7 +552,7 @@ class SemClass implements ArrayAccess
             $db = DBManager::get();
             self::$sem_classes = [];
 
-            $cache = StudipCacheFactory::getCache();
+            $cache = \Studip\Cache\Factory::getCache();
             $class_array = unserialize($cache->read('DB_SEM_CLASSES_ARRAY'));
             if (!$class_array) {
 
@@ -576,7 +564,7 @@ class SemClass implements ArrayAccess
                     $class_array = $statement->fetchAll(PDO::FETCH_ASSOC);
 
                     if ($class_array) {
-                        $cache = StudipCacheFactory::getCache();
+                        $cache = \Studip\Cache\Factory::getCache();
                         $cache->write('DB_SEM_CLASSES_ARRAY', serialize($class_array));
                     }
                 } catch (PDOException $e) {
@@ -605,7 +593,7 @@ class SemClass implements ArrayAccess
      */
     static public function refreshClasses()
     {
-        StudipCacheFactory::getCache()->expire('DB_SEM_CLASSES_ARRAY');
+        \Studip\Cache\Factory::getCache()->expire('DB_SEM_CLASSES_ARRAY');
         self::$sem_classes = null;
         return self::getClasses();
     }
diff --git a/lib/classes/SemType.class.php b/lib/classes/SemType.php
index 3d5de5d..5be1f19 100644
--- a/lib/classes/SemType.class.php
+++ b/lib/classes/SemType.php
@@ -68,7 +68,7 @@ class SemType implements ArrayAccess
                 "chdate = UNIX_TIMESTAMP() " .
             "WHERE id = :id ".
         "");
-        StudipCacheFactory::getCache()->expire('DB_SEM_TYPES_ARRAY');
+        \Studip\Cache\Factory::getCache()->expire('DB_SEM_TYPES_ARRAY');
         return $statement->execute([
             'id' => $this->data['id'],
             'name' => $this->data['name'],
@@ -86,10 +86,10 @@ class SemType implements ArrayAccess
         if ($this->countSeminars() === 0) {
             $db = DBManager::get();
             $statement = $db->prepare("
-                DELETE FROM sem_types 
-                WHERE id = :id 
+                DELETE FROM sem_types
+                WHERE id = :id
             ");
-            StudipCacheFactory::getCache()->expire('DB_SEM_TYPES_ARRAY');
+            \Studip\Cache\Factory::getCache()->expire('DB_SEM_TYPES_ARRAY');
             return $statement->execute([
                 'id' => $this->data['id']
             ]);
@@ -119,11 +119,9 @@ class SemType implements ArrayAccess
      * deprecated, does nothing, should not be used
      * @param string $offset
      * @param mixed $value
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
+
+    public function offsetSet($offset, $value): void
     {
     }
 
@@ -131,12 +129,8 @@ class SemType implements ArrayAccess
      * Compatibility function with old $SEM_TYPE variable for plugins. Maps the
      * new array-structure to the old boolean values.
      * @param integer $offset: name of attribute
-     * @return boolean|(localized)string
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         switch ($offset) {
             case "name":
@@ -153,12 +147,8 @@ class SemType implements ArrayAccess
     /**
      * ArrayAccess method to check if an attribute exists.
      * @param mixed $offset
-     * @return bool
-     *
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return isset($this->data[$offset]);
     }
@@ -166,11 +156,8 @@ class SemType implements ArrayAccess
     /**
      * deprecated, does nothing, should not be used
      * @param string $offset
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
     }
 
@@ -188,7 +175,7 @@ class SemType implements ArrayAccess
             $db = DBManager::get();
             self::$sem_types = [];
 
-            $cache = StudipCacheFactory::getCache();
+            $cache = \Studip\Cache\Factory::getCache();
             $types_array = unserialize($cache->read('DB_SEM_TYPES_ARRAY'));
             if (!$types_array) {
                 try {
@@ -198,7 +185,7 @@ class SemType implements ArrayAccess
                     $statement->execute();
                     $types_array = $statement->fetchAll(PDO::FETCH_ASSOC);
                     if ($types_array) {
-                        $cache = StudipCacheFactory::getCache();
+                        $cache = \Studip\Cache\Factory::getCache();
                         $cache->write('DB_SEM_TYPES_ARRAY', serialize($types_array));
                     }
                 } catch (PDOException $e) {
@@ -223,7 +210,7 @@ class SemType implements ArrayAccess
 
     static public function refreshTypes() {
         self::$sem_types = null;
-        StudipCacheFactory::getCache()->expire('DB_SEM_TYPES_ARRAY');
+        \Studip\Cache\Factory::getCache()->expire('DB_SEM_TYPES_ARRAY');
         return self::getTypes();
     }
 
diff --git a/lib/classes/Seminar.class.php b/lib/classes/Seminar.php
index 054c337..0fccdbc 100644
--- a/lib/classes/Seminar.class.php
+++ b/lib/classes/Seminar.php
@@ -4,7 +4,7 @@
 # Lifter007: TODO
 # Lifter010: TODO
 /**
- * Seminar.class.php - This class represents a Seminar in Stud.IP
+ * Seminar.php - This class represents a Seminar in Stud.IP
  *
  * This class provides functions for seminar-members, seminar-dates, and seminar-modules
  *
@@ -303,7 +303,7 @@ class Seminar
     {
 
         // Caching
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         $cache_key = 'course/undecorated_data/'. $this->id;
 
         if ($filter) {
@@ -745,7 +745,7 @@ class Seminar
         StudipLog::log("SEM_ADD_SINGLEDATE", $this->getId(), $singledate->toString(), 'SingleDateID: '.$singledate->getTerminID());
         // logging <<<<<<
 
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         $cache->expire('course/undecorated_data/'. $this->getId());
 
         $this->readSingleDates();
@@ -1565,7 +1565,7 @@ class Seminar
         SeminarCycleDate::deleteBySQL('seminar_id = ' . DBManager::get()->quote($s_id));
 
         // Alle weiteren Postings zu diesem Seminar in den Forums-Modulen löschen
-        foreach (PluginEngine::getPlugins('ForumModule') as $plugin) {
+        foreach (PluginEngine::getPlugins(ForumModule::class) as $plugin) {
             $plugin->deleteContents($s_id);  // delete content irrespective of plugin-activation in the seminar
 
             if ($plugin->isActivated($s_id)) {   // only show a message, if the plugin is activated, to not confuse the user
@@ -1735,7 +1735,7 @@ class Seminar
      */
     public function getDatesTemplate($template, $params = [])
     {
-        if (!$template instanceof Flexi_Template && is_string($template)) {
+        if (!$template instanceof Flexi\Template && is_string($template)) {
             $template = $GLOBALS['template_factory']->open($template);
         }
 
diff --git a/lib/classes/SeminarCategories.class.php b/lib/classes/SeminarCategories.php
index 5302f1e..25eb4c1 100644
--- a/lib/classes/SeminarCategories.class.php
+++ b/lib/classes/SeminarCategories.php
@@ -3,7 +3,7 @@
 # Lifter003: TODO
 # Lifter010: TODO
 /**
- * SeminarCategories.class.php
+ * SeminarCategories.php
  *
  * encapsulates configuration settings for courses from config.inc.php
  * aka $SEM_CLASS, $SEM_TYPE, $UPLOAD_TYPES
@@ -14,7 +14,7 @@
  */
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// SeminarCategories.class.php
+// SeminarCategories.php
 //
 // Copyright (C) 2008 André Noack <noack@data-quest>, data-quest GmbH <info@data-quest.de>
 // +---------------------------------------------------------------------------+
diff --git a/lib/classes/SessionDecoder.class.php b/lib/classes/SessionDecoder.php
index 8c0bc6b..fc40c07 100644
--- a/lib/classes/SessionDecoder.class.php
+++ b/lib/classes/SessionDecoder.php
@@ -3,7 +3,7 @@
 # Lifter003: TODO
 # Lifter010: TODO
 /**
- * SessionDecoder.class.php
+ * SessionDecoder.php
  *
  * decodes serialized PHP session data
  *
@@ -13,7 +13,7 @@
  */
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// SessionDecoder.class.php
+// SessionDecoder.php
 //
 // Copyright (C) 2008 André Noack <noack@data-quest>, data-quest GmbH <info@data-quest.de>
 // +---------------------------------------------------------------------------+
@@ -83,69 +83,42 @@ class SessionDecoder implements ArrayAccess, Countable, Iterator {
         return $this->var_names;
     }
 
-    /**
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function rewind()
+    public function rewind(): void
     {
         reset($this->var_names);
     }
 
-    /**
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function current()
+    public function current(): mixed
     {
         $current = current($this->var_names);
         return $current !== false ? $this->offsetGet($current) : false;
     }
 
-    /**
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function key()
+    public function key(): mixed
     {
         return current($this->var_names);
     }
 
-    /**
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function next()
+    public function next(): void
     {
         next($this->var_names);
     }
 
-    /**
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function valid()
+    public function valid(): bool
     {
         $current = current($this->var_names);
         return $current !== false;
     }
 
-    /**
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return isset($this->encoded_session[$offset]);
     }
 
     /**
-     * @param $offset
-     * @return mixed|null
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
+     * @param string $offset
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         if($this->offsetExists($offset) && !isset($this->decoded_session[$offset])) {
             $this->decoded_session[$offset] = unserialize($this->encoded_session[$offset]);
@@ -153,27 +126,15 @@ class SessionDecoder implements ArrayAccess, Countable, Iterator {
         return $this->decoded_session[$offset] ?? null;
     }
 
-    /**
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
     }
 
-    /**
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
     }
 
-    /**
-     * @todo Add int return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function count()
+    public function count(): int
     {
         return count($this->var_names);
     }
diff --git a/lib/classes/SimpleCollection.php b/lib/classes/SimpleCollection.php
new file mode 100644
index 0000000..ae773f5
--- /dev/null
+++ b/lib/classes/SimpleCollection.php
@@ -0,0 +1,782 @@
+<?php
+if (!defined('SORT_NATURAL')) {
+    define('SORT_NATURAL', 6);
+}
+if (!defined('SORT_FLAG_CASE')) {
+    define('SORT_FLAG_CASE', 8);
+}
+
+/**
+ * SimpleCollection.php
+ * collection of assoc arrays with convenience
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      André Noack <noack@data-quest.de>
+ * @copyright   2013 Stud.IP Core-Group
+ * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
+ * @category    Stud.IP
+ *
+ * @template T
+ */
+class SimpleCollection extends StudipArrayObject
+{
+    /**
+     * callable to initialize collection
+     *
+     * @var ?callable(): array<T>
+     */
+    protected $finder;
+
+    /**
+     * number of records after last init
+     *
+     * @var int
+     */
+    protected $last_count;
+
+    /**
+     * collection with deleted records
+     * @var static
+     */
+    protected $deleted;
+
+    /**
+     * creates a collection from an array of arrays
+     * all arrays should contain same keys, but is not enforced
+     *
+     * @param array<T> $data array containing assoc arrays
+     * @return SimpleCollection<T>
+     */
+    public static function createFromArray(array $data)
+    {
+        return new self($data);
+    }
+
+    /**
+     * converts arrays or objects to ArrayObject objects
+     * if ArrayAccess interface is not available
+     *
+     * @param mixed $a
+     * @return StudipArrayObject|ArrayAccess
+     */
+    public static function arrayToArrayObject($a)
+    {
+        if ($a instanceof StudipArrayObject) {
+            $a->setFlags(StudipArrayObject::ARRAY_AS_PROPS);
+            return $a;
+        }
+
+        if ($a instanceof ArrayObject) {
+            return new StudipArrayObject($a->getArrayCopy(), StudipArrayObject::ARRAY_AS_PROPS);
+        }
+
+        if ($a instanceof ArrayAccess) {
+            return $a;
+        }
+
+        return new StudipArrayObject((array) $a, StudipArrayObject::ARRAY_AS_PROPS);
+    }
+
+    /**
+     * returns closure to compare a value against given arguments
+     * using given operator
+     *
+     * @param string|callable(mixed, mixed|array): bool  $operator
+     * @param mixed|array $args
+     * @throws InvalidArgumentException
+     * @return callable(mixed): bool comparison function
+     */
+    public static function getCompFunc($operator, $args)
+    {
+        if (is_callable($operator)) {
+            $comp_func = function ($a) use ($args, $operator) {
+                return $operator($a, $args);
+            };
+        } else {
+            if (!is_array($args)) {
+                $args = [$args];
+            }
+            switch ($operator) {
+                case '==':
+                    $comp_func = function ($a) use ($args) {
+                        return in_array($a, $args);
+                    };
+                break;
+                case '===':
+                    $comp_func = function ($a) use ($args) {
+                        return in_array($a, $args, true);
+                    };
+                break;
+                case '!=':
+                case '<>':
+                    $comp_func = function ($a) use ($args) {
+                        return !in_array($a, $args);
+                    };
+                break;
+                case '!==':
+                    $comp_func = function ($a) use ($args) {
+                        return !in_array($a, $args, true);
+                    };
+                break;
+                case '<':
+                case '>':
+                case '<=':
+                case '>=':
+                    $op_func = function ($a, $b) use ($operator) {
+                        if ($operator === '<') {
+                            return $a < $b;
+                        } elseif ($operator === '<=') {
+                            return $a <= $b;
+                        } elseif ($operator === '>=') {
+                            return $a >= $b;
+                        } elseif ($operator === '>') {
+                            return $a > $b;
+                        }
+                    };
+                    $comp_func = function ($a) use ($op_func, $args) {
+                        return $op_func($a, $args[0]);
+                    };
+                break;
+                case '><':
+                    $comp_func = function ($a) use ($args) {
+                        return $a > $args[0] && $a < $args[1];
+                    };
+                break;
+                case '>=<=':
+                    $comp_func = function ($a) use ($args) {
+                        return $a >= $args[0] && $a <= $args[1];
+                    };
+                    break;
+                case '%=':
+                    $comp_func = function ($a) use ($args) {
+                        $a = mb_strtolower(static::translitLatin1($a));
+                        $args = array_map([static::class, 'translitLatin1'], $args);
+                        $args = array_map('mb_strtolower', $args);
+                        return in_array($a, $args);
+                    };
+                break;
+                case '*=':
+                    $comp_func = function ($a) use ($args) {
+                        foreach ($args as $arg) {
+                            if (mb_strpos($a, $arg) !== false) {
+                                return true;
+                            }
+                        }
+                        return false;
+                    };
+                break;
+                case '^=':
+                    $comp_func = function ($a) use ($args) {
+                        foreach ($args as $arg) {
+                            if (mb_strpos($a, $arg) === 0) {
+                                return true;
+                            }
+                        }
+                        return false;
+                    };
+                break;
+                case '$=':
+                    $comp_func = function ($a) use ($args) {
+                        foreach ($args as $arg) {
+                            $found = mb_strrpos($a, $arg);
+                            if ($found !== false && ($found + mb_strlen($arg)) === mb_strlen($a)) {
+                                return true;
+                            }
+                        }
+                        return false;
+                    };
+                break;
+                case '~=':
+                    $comp_func = function ($a) use ($args) {
+                        foreach ($args as $arg) {
+                            if (preg_match($arg, $a) === 1) {
+                                return true;
+                            }
+                        }
+                        return false;
+                    };
+                    break;
+                default:
+                    throw new InvalidArgumentException('unknown operator: ' . $operator);
+             }
+         }
+         return $comp_func;
+    }
+
+    /**
+     * transliterates latin1 string to ascii
+     *
+     * @param string $text
+     * @return string
+     */
+    public static function translitLatin1($text)
+    {
+        if (!preg_match('/[\200-\377]/', $text)) {
+            return $text;
+        }
+        $text = str_replace(['ä','Ä','ö','Ö','ü','Ü','ß'], ['a','A','o','O','u','U','s'], $text);
+        $text = str_replace(['À','Á','Â','Ã','Å','Æ'], 'A' , $text);
+        $text = str_replace(['à','á','â','ã','å','æ'], 'a' , $text);
+        $text = str_replace(['È','É','Ê','Ë'], 'E' , $text);
+        $text = str_replace(['è','é','ê','ë'], 'e' , $text);
+        $text = str_replace(['Ì','Í','Î','Ï'], 'I' , $text);
+        $text = str_replace(['ì','í','î','ï'], 'i' , $text);
+        $text = str_replace(['Ò','Ó','Õ','Ô','Ø'], 'O' , $text);
+        $text = str_replace(['ò','ó','ô','õ','ø'], 'o' , $text);
+        $text = str_replace(['Ù','Ú','Û'], 'U' , $text);
+        $text = str_replace(['ù','ú','û'], 'u' , $text);
+        $text = str_replace(['Ç','ç','Ð','Ñ','Ý','ñ','ý','ÿ'], ['C','c','D','N','Y','n','y','y'] , $text);
+        return $text;
+    }
+
+    /**
+     * Constructor
+     *
+     * @param array<T>|callable(): array<T> $data array or closure to fill collection
+     */
+    public function __construct($data = [])
+    {
+        parent::__construct();
+        $this->finder = is_callable($data) ? $data : null;
+        $this->deleted = clone $this;
+        if (is_callable($data)) {
+            $this->refresh();
+        } else {
+            $this->exchangeArray($data);
+        }
+    }
+
+    /**
+     * @param array $input
+     * @return array
+     */
+    public function exchangeArray($input)
+    {
+        return parent::exchangeArray(array_map(
+            [static::class, 'arrayToArrayObject'],
+            $input
+        ));
+    }
+
+    /**
+     * converts the object and all elements to plain arrays
+     *
+     * @return array
+     */
+    public function toArray()
+    {
+        $args = func_get_args();
+        return $this->map(function ($a) use ($args) {
+            if (method_exists($a, 'toArray')) {
+                return call_user_func_array([$a, 'toArray'], $args);
+            }
+            if (method_exists($a, 'getArrayCopy')) {
+                return $a->getArrayCopy();
+            }
+            return (array) $a;
+        }
+        );
+    }
+
+    /**
+     *
+     * @see ArrayObject::append()
+     */
+    public function append($newval)
+    {
+        parent::append(static::arrayToArrayObject($newval));
+    }
+
+    /**
+     * Sets the value at the specified index
+     * ensures the value has ArrayAccess
+     *
+     * @param mixed $index
+     * @param mixed $newval
+     *
+     * @see ArrayObject::offsetSet()
+     */
+
+    public function offsetSet($index, $newval): void
+    {
+        if (is_numeric($index)) {
+            $index = (int) $index;
+        }
+        parent::offsetSet($index, static::arrayToArrayObject($newval));
+    }
+
+    /**
+     * Unsets the value at the specified index
+     * value is moved to internal deleted collection
+     *
+     * @see ArrayObject::offsetUnset()
+     * @throws InvalidArgumentException
+     */
+    public function offsetUnset($index): void
+    {
+        if ($this->offsetExists($index)) {
+            $this->deleted[] = $this->offsetGet($index);
+        }
+        parent::offsetUnset($index);
+    }
+
+    /**
+     * sets the finder function
+     *
+     * @param callable(): array<T> $finder
+     * @return void
+     */
+    public function setFinder(callable $finder)
+    {
+        $this->finder = $finder;
+    }
+
+    /**
+     * get deleted records collection
+     * @return SimpleCollection<T>
+     */
+    public function getDeleted()
+    {
+        return $this->deleted;
+    }
+
+    /**
+     * reloads the elements of the collection
+     * by calling the finder function
+     *
+     * @return ?int of records after refresh
+     */
+    public function refresh()
+    {
+        if (is_callable($this->finder)) {
+            $data = call_user_func($this->finder);
+            $this->exchangeArray($data);
+            $this->deleted->exchangeArray([]);
+            return $this->last_count = $this->count();
+        }
+    }
+
+    /**
+     * returns a new collection containing all elements
+     * where given columns value matches given value(s) using passed operator
+     * pass array for multiple values
+     *
+     * operators:
+     * == equal, like php
+     * === identical, like php
+     * !=,<> not equal, like php
+     * !== not identical, like php
+     * <,>,<=,>= less,greater,less or equal,greater or equal
+     * >< between without borders, needs two arguments
+     * >=<= between including borders, needs two arguments
+     * %= like string, transliterate to ascii,case insensitive
+     * *= contains string
+     * ^= begins with string
+     * $= ends with string
+     * ~= regex
+     *
+     * @param string $key the column name
+     * @param mixed $values value to search for
+     * @param string|callable $op operator to find
+     * @return SimpleCollection<T> with found records
+     */
+    public function findBy($key, $values, $op = '==')
+    {
+        $comp_func = self::getCompFunc($op, $values);
+        return $this->filter(function ($record) use ($comp_func, $key) {
+            return $comp_func($record[$key]);
+        });
+    }
+
+    /**
+     * returns the first element
+     * where given column has given value(s)
+     * pass array for multiple values
+     *
+     * @param string $key the column name
+     * @param mixed $values value to search for,
+     * @param string|callable $op operator to find
+     * @return ?T found record
+     */
+    public function findOneBy($key, $values, $op = '==')
+    {
+        $comp_func = self::getCompFunc($op, $values);
+        return $this->filter(function ($record) use ($comp_func, $key) {
+            return $comp_func($record[$key]);
+        }, 1)->first();
+    }
+
+    /**
+     * apply given callback to all elements of
+     * collection
+     *
+     * @param callable(T): int $func the function to call
+     * @return int|false addition of return values
+     */
+    public function each(callable $func)
+    {
+        $result = false;
+        foreach ($this->storage as $record) {
+            $result += call_user_func($func, $record);
+        }
+        return $result;
+    }
+
+    /**
+     * apply given callback to all elements of
+     * collection and give back array of return values
+     *
+     * @param callable(T, mixed): mixed $func the function to call
+     * @return array<mixed>
+     */
+    public function map(callable $func)
+    {
+        $results = [];
+        foreach ($this->storage as $key => $value) {
+            $results[$key] = call_user_func($func, $value, $key);
+        }
+        return $results;
+    }
+
+    /**
+     * filter elements
+     * if given callback returns true
+     *
+     * @param ?callable(T, mixed): bool $func the function to call
+     * @param ?integer $limit limit number of found records
+     * @return SimpleCollection<T> containing filtered elements
+     */
+    public function filter(callable $func = null, $limit = null)
+    {
+        $results = [];
+        $found = 0;
+        foreach ($this->storage as $key => $value) {
+            if (call_user_func($func, $value, $key)) {
+                $results[$key] = $value;
+                if ($limit && (++$found == $limit)) {
+                    break;
+                }
+            }
+        }
+        return self::createFromArray($results);
+    }
+
+    /**
+     * Returns whether any element of the collection returns true for the
+     * given callback.
+     *
+     * @param  callable(T, mixed): bool $func the function to call
+     * @return bool
+     */
+    public function any(callable $func)
+    {
+        foreach ($this->storage as $key => $value) {
+            if (call_user_func($func, $value, $key)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Returns whether every element of the collection returns true for the
+     * given callback.
+     *
+     * @param  callable(T, mixed): bool $func the function to call
+     * @return bool
+     */
+    public function every(callable $func)
+    {
+        foreach ($this->storage as $key => $value) {
+            if (!call_user_func($func, $value, $key)) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    /**
+     * extract array of columns values
+     * pass array or space-delimited string for multiple columns
+     *
+     * @param string|array $columns the column(s) to extract
+     * @return array of extracted values
+     */
+    public function pluck($columns)
+    {
+        if (!is_array($columns)) {
+            $columns = words($columns);
+        }
+        $func = function ($r) use ($columns) {
+            $result = [];
+            foreach ($columns as $c) {
+                $result[] = $r[$c];
+            }
+            return $result;
+        };
+        $result = $this->map($func);
+        return count($columns) === 1 ? array_map('current', $result) : $result;
+    }
+
+    /**
+     * returns the collection as grouped array
+     * first param is the column to group by, it becomes the key in
+     * the resulting array, default is pk. Limit returned fields with second param
+     * The grouped entries can optoionally go through the given
+     * callback. If no callback is provided, only the first grouped
+     * entry is returned, suitable for grouping by unique column
+     *
+     * @param string $group_by the column to group by, pk if ommitted
+     * @param string|array|null $only_these_fields limit returned fields
+     * @param ?callable $group_func closure to aggregate grouped entries
+     * @return array assoc array
+     */
+    public function toGroupedArray($group_by = 'id', $only_these_fields = null, callable $group_func = null)
+    {
+        $result = [];
+        if (is_string($only_these_fields)) {
+            $only_these_fields = words($only_these_fields);
+        }
+        foreach ($this->toArray() as $record) {
+            $key = $record[$group_by];
+            $ret = [];
+            if (is_array($only_these_fields)) {
+                $result[$key][] = array_intersect_key($record, array_flip($only_these_fields));
+            } else {
+                $result[$key][] = $record;
+            }
+        }
+        if ($group_func === null) {
+            $group_func = 'current';
+        }
+        return array_map($group_func, $result);
+    }
+
+    /**
+     * get the first element
+     *
+     * @return ?T first element or null
+     */
+    public function first()
+    {
+        $keys = array_keys($this->storage);
+        $first_offset = reset($keys);
+        return $this->offsetGet($first_offset ?: 0);
+    }
+
+    /**
+     * get the last element
+     *
+     * @return ?T last element or null
+     */
+    public function last()
+    {
+        $keys = array_keys($this->storage);
+        $last_offset = end($keys);
+        return $this->offsetGet($last_offset ?: 0);
+    }
+
+     /**
+     * get the the value from given key from first element
+     *
+     * @param string $key
+     * @return mixed
+     */
+    public function val($key)
+    {
+        $first = $this->first();
+        return $first[$key] ?? null;
+    }
+
+    /**
+     * mark element(s) for deletion
+     * where given column has given value(s)
+     * element(s) are moved to
+     * internal deleted collection
+     * pass array for multiple values
+     *
+     * operators:
+     * == equal, like php
+     * === identical, like php
+     * !=,<> not equal, like php
+     * !== not identical, like php
+     * <,>,<=,>= less,greater,less or equal,greater or equal
+     * >< between without borders, needs two arguments
+     * >=<= between including borders, needs two arguments
+     * %= like string, transliterate to ascii,case insensitive
+     * *= contains string
+     * ^= begins with string
+     * $= ends with string
+     * ~= regex
+     *
+     * @param string $key
+     * @param mixed $values
+     * @param string|callable(mixed, mixed|array): bool $op operator to find elements
+     * @return int|false number of unsetted elements
+     */
+    public function unsetBy($key, $values, $op = '==')
+    {
+        $ret = false;
+        $comp_func = self::getCompFunc($op, $values);
+        foreach ($this->storage as $k => $record) {
+            if ($comp_func($record[$key])) {
+                $this->offsetunset($k);
+                $ret += 1;
+            }
+        }
+        return $ret;
+    }
+
+    /**
+     * sorts the collection by columns of contained elements and returns it
+     *
+     * works like sql order by:
+     * first param is a string containing combinations of column names
+     * and sort direction, separated by comma e.g.
+     *  'name asc, nummer desc '
+     *  sorts first by name ascending and then by nummer descending
+     *  second param denotes the sort type (using PHP sort constants):
+     *  SORT_LOCALE_STRING:
+     *  compare items as strings, transliterate latin1 to ascii, case insensitiv, natural order for numbers
+     *  SORT_NUMERIC:
+     *  compare items as integers
+     *  SORT_STRING:
+     *  compare items as strings
+     *  SORT_NATURAL:
+     *  compare items as strings using "natural ordering"
+     *  SORT_FLAG_CASE:
+     *  can be combined (bitwise OR) with SORT_STRING or SORT_NATURAL to sort strings case-insensitively
+     *
+     * @param string $order columns to order by
+     * @param integer $sort_flags
+     * @return $this the sorted collection
+     */
+    public function orderBy($order, $sort_flags = SORT_LOCALE_STRING)
+    {
+        //('name asc, nummer desc ')
+        $sort_locale = false;
+        switch ($sort_flags) {
+        case SORT_NATURAL:
+            $sort_func = 'strnatcmp';
+            break;
+        case SORT_NATURAL | SORT_FLAG_CASE:
+            $sort_func = 'strnatcasecmp';
+            break;
+        case SORT_STRING | SORT_FLAG_CASE:
+            $sort_func = 'strcasecmp';
+            break;
+        case SORT_STRING:
+            $sort_func = 'strcmp';
+            break;
+        case SORT_NUMERIC:
+            $sort_func = function ($a, $b) {
+                return (int) $a - (int) $b;
+            };
+            break;
+        case SORT_LOCALE_STRING:
+        default:
+            $sort_func = 'strnatcasecmp';
+            $sort_locale = true;
+        }
+
+        $sorter = [];
+        foreach (explode(',', $order) as $one) {
+            $sorter[] = array_values(array_filter(array_map('trim', explode(' ', $one))));
+        }
+
+        $func = function ($d1, $d2) use ($sorter, $sort_func, $sort_locale) {
+            do {
+                $current_sorter = current($sorter);
+                $field = $current_sorter[0];
+                $dir = $current_sorter[1] ?? '';
+                if (!$sort_locale) {
+                    $value1 = $d1[$field];
+                    $value2 = $d2[$field];
+                } else {
+                    $value1 = static::translitLatin1(mb_substr($d1[$field], 0, 100));
+                    $value2 = static::translitLatin1(mb_substr($d2[$field], 0, 100));
+                }
+                $ret = $sort_func($value1, $value2);
+                if (strtolower($dir) == 'desc') $ret = $ret * -1;
+            } while ($ret === 0 && next($sorter));
+
+            return $ret;
+        };
+        if (count($sorter)) {
+            $this->uasort($func);
+        }
+        return $this;
+    }
+
+    /**
+     * returns a new collection contaning a sequence of original collection
+     * mimics the sql limit constrain:
+     * used with one parameter, the first x elements are extracted
+     * used with two parameters, the first parameter denotes the offset, the second the
+     * number of elements
+     *
+     * @param integer $arg1
+     * @param ?integer $arg2
+     * @return SimpleCollection<T>
+     */
+    public function limit($arg1, $arg2 = null)
+    {
+        if (is_null($arg2)) {
+            if ($arg1 > 0) {
+                $row_count = $arg1;
+                $offset = 0;
+            } else {
+                $row_count = abs($arg1);
+                $offset = $arg1;
+            }
+        } else {
+            $offset = $arg1;
+            $row_count = $arg2;
+        }
+        return self::createFromArray(array_slice($this->storage, $offset, $row_count, true));
+    }
+
+     /**
+     * calls the given method on all elements
+     * of the collection
+     * @param literal-string $method methodname to call
+     * @param array $params parameters for methodcall
+     * @return array of all return values
+     */
+    public function sendMessage($method, $params = []) {
+        $results = [];
+        foreach ($this->storage as $record) {
+            $results[] = call_user_func_array([$record, $method], $params);
+        }
+        return $results;
+    }
+
+    /**
+     * magic version of sendMessage
+     * calls undefineds methods on all elements of the collection
+     * But beware of the dark side...
+     *
+     * @param literal-string $method methodname to call
+     * @param array $params parameters for methodcall
+     * @return array of all return values
+     */
+    public function __call($method, $params)
+    {
+        return $this->sendMessage($method, $params);
+    }
+
+    /**
+     * merge in another collection, elements are appended
+     *
+     * @param SimpleCollection<T> $a_collection
+     * @return void
+     */
+    public function merge(SimpleCollection $a_collection)
+    {
+        $this->storage = array_merge($this->storage, $a_collection->getArrayCopy());
+    }
+}
diff --git a/lib/classes/SimpleORMap.php b/lib/classes/SimpleORMap.php
new file mode 100644
index 0000000..7492906
--- /dev/null
+++ b/lib/classes/SimpleORMap.php
@@ -0,0 +1,2483 @@
+<?php
+/**
+ * SimpleORMap.php
+ * simple object-relational mapping
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      André Noack <noack@data-quest.de>
+ * @copyright   2010 Stud.IP Core-Group
+ * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
+ * @category    Stud.IP
+*/
+
+class SimpleORMap implements ArrayAccess, Countable, IteratorAggregate
+{
+    /**
+     * Defines `_` as character used when joining composite primary keys.
+     */
+    const ID_SEPARATOR = '_';
+
+    /**
+     * table row data
+     * @var array $content
+     */
+    protected $content = [];
+
+    /**
+     * table row data
+     * @var array $content_db
+     */
+    protected $content_db = [];
+
+    /**
+     * new state of entry
+     * @var boolean $is_new
+     */
+    protected $is_new = true;
+
+    /**
+     * deleted state of entry
+     * @var boolean $is_deleted
+     */
+    protected $is_deleted = false;
+
+     /**
+     * db table metadata
+     * @var ?array $schemes;
+     */
+    public static $schemes = null;
+
+    /**
+     * configuration data for subclasses
+     * @see self::configure()
+     * @var array $config;
+     */
+    protected static $config = [];
+
+    /**
+     * stores instantiated related objects
+     * @var array $relations
+     */
+    protected $relations = [];
+
+    /**
+     * assoc array for storing values for additional fields
+     *
+     * @var array $additional_data
+     */
+    protected $additional_data = [];
+
+    /**
+     * reserved indentifiers, fields with those names must not have an explicit getXXX() method
+     * @var array $reserved_slots
+     */
+    protected static $reserved_slots = ['value','newid','iterator','tablemetadata', 'relationvalue','wherequery','relationoptions','data','new','id'];
+
+    /**
+     * indicator for batch operations in findEachBySQL
+     *
+     * @var bool $performs_batch_operation
+     */
+    protected static $performs_batch_operation = false;
+
+    /**
+     * name of db table
+     * @return string
+     */
+    protected static function db_table()
+    {
+        return static::config('db_table');
+    }
+
+    /**
+     * table columns
+     * @return array
+     */
+    protected static function db_fields()
+    {
+        return static::config('db_fields');
+    }
+
+    /**
+     * primary key columns
+     * @return array
+     */
+    protected static function pk()
+    {
+        return static::config('pk');
+    }
+
+    /**
+     * default values for columns
+     * @return array
+     */
+    protected static function default_values()
+    {
+        return static::config('default_values');
+    }
+
+    /**
+     * list of columns to deserialize
+     * @return array key is name of column, value is name of ArrayObject class
+     */
+    protected static function serialized_fields()
+    {
+        return static::config('serialized_fields');
+    }
+
+    /**
+     * aliases for columns
+     * alias => column
+     * @return array
+     */
+    protected static function alias_fields()
+    {
+        return static::config('alias_fields');
+    }
+
+    /**
+     * multi-language fields
+     * name => boolean
+     * @return array
+     */
+    protected static function i18n_fields()
+    {
+        return static::config('i18n_fields');
+    }
+
+    /**
+     * additional computed fields
+     * name => callable
+     * @return array
+     */
+    protected static function additional_fields()
+    {
+        return static::config('additional_fields');
+    }
+
+    /**
+     * 1:n relation
+     * @return array
+     */
+    protected static function has_many()
+    {
+        return static::config('has_many');
+    }
+
+    /**
+     * 1:1 relation
+     * @return array
+     */
+    protected static function has_one()
+    {
+        return static::config('has_one');
+    }
+
+    /**
+     * n:1 relations
+     * @return array
+     */
+    protected static function belongs_to()
+    {
+        return static::config('belongs_to');
+    }
+
+    /**
+     * n:m relations
+     * @return array
+     */
+    protected static function has_and_belongs_to_many()
+    {
+        return static::config('has_and_belongs_to_many');
+    }
+
+    /**
+     * callbacks
+     * @return array<string, array<string|Closure>>
+     */
+    protected static function registered_callbacks()
+    {
+        return static::config('registered_callbacks');
+    }
+
+    /**
+     * contains an array of all used identifiers for fields
+     * (db columns + aliased columns + additional columns + relations)
+     * @return array
+     */
+    protected static function known_slots()
+    {
+        return static::config('known_slots');
+    }
+
+    /**
+     * assoc array used to map SORM callback to NotificationCenter
+     * keys are SORM callbacks, values notifications
+     * eg. 'after_create' => 'FooDidCreate'
+     *
+     * @return array
+     */
+    protected static function notification_map()
+    {
+        return static::config('notification_map');
+    }
+
+    /**
+     * assoc array for mapping get/set Methods
+     *
+     * @return array
+     */
+    protected static function getter_setter_map()
+    {
+        return static::config('getter_setter_map');
+    }
+
+    //////////////////////////////////////////////////
+
+    /**
+     * set configuration data from subclass
+     *
+     * @param ?array $config configuration data
+     * @return void
+     */
+    protected static function configure($config = [])
+    {
+        $class = static::class;
+
+        if (empty($config['db_table'])) {
+            $config['db_table'] = strtolower($class);
+        }
+
+        if (!isset($config['db_fields'])) {
+            if (static::tableScheme($config['db_table'])) {
+                $config['db_fields'] = self::$schemes[$config['db_table']]['db_fields'];
+                $config['pk'] = self::$schemes[$config['db_table']]['pk'];
+            }
+        }
+
+        if (isset($config['pk'])
+            && !isset($config['db_fields']['id'])
+            && !isset($config['alias_fields']['id'])
+            && !isset($config['additional_fields']['id'])
+        ) {
+            if (count($config['pk']) === 1) {
+                $config['alias_fields']['id'] = $config['pk'][0];
+            } else {
+                $config['additional_fields']['id'] = ['get' => '_getId',
+                                                           'set' => '_setId'];
+            }
+        }
+        if (isset($config['additional_fields'])) {
+            foreach ($config['additional_fields'] as $a_field => $a_config) {
+                if (is_array($a_config) && !(isset($a_config['get']) || isset($a_config['set']))) {
+                    $relation = $a_config[0] ?? '';
+                    $relation_field = $a_config[1] ?? '';
+                    if (!$relation) {
+                        [$relation, $relation_field] = explode('_', $a_field);
+                    }
+                    if (!$relation_field || !$relation) {
+                        throw new UnexpectedValueException('no relation found for autoget/set additional field: ' . $a_field);
+                    }
+                    $config['additional_fields'][$a_field] = ['get'            => '_getAdditionalValueFromRelation',
+                                                                   'set'            => '_setAdditionalValue',
+                                                                   'relation'       => $relation,
+                                                                   'relation_field' => $relation_field];
+                }
+            }
+        }
+        if (isset($config['serialized_fields'])) {
+            foreach ($config['serialized_fields'] as $a_field => $object_type) {
+                if (!(is_subclass_of($object_type, 'StudipArrayObject'))) {
+                    throw new UnexpectedValueException(sprintf('serialized field %s must use subclass of StudipArrayObject', $a_field));
+                }
+            }
+        }
+
+        foreach (['default_values', 'serialized_fields', 'alias_fields', 'i18n_fields', 'additional_fields'] as $fields) {
+            if (!isset($config[$fields])) {
+                $config[$fields] = [];
+            }
+        }
+
+        foreach (['has_many', 'belongs_to', 'has_one', 'has_and_belongs_to_many'] as $type) {
+            if (isset($config[$type]) && is_array($config[$type])) {
+                foreach (array_keys($config[$type]) as $one) {
+                    $config['relations'][$one] = null;
+                }
+            } else {
+                $config[$type] = [];
+            }
+        }
+
+        $callbacks = ['before_create',
+                      'before_update',
+                      'before_store',
+                      'before_delete',
+                      'before_initialize',
+                      'after_create',
+                      'after_update',
+                      'after_store',
+                      'after_delete',
+                      'after_initialize'];
+
+        foreach ($callbacks as $callback) {
+            if (!isset($config['registered_callbacks'][$callback])) {
+                $config['registered_callbacks'][$callback] = [];
+            }
+        }
+
+        $auto_notification_map['after_create'] = $class . 'DidCreate';
+        $auto_notification_map['after_store'] = $class . 'DidStore';
+        $auto_notification_map['after_delete'] = $class . 'DidDelete';
+        $auto_notification_map['after_update'] = $class . 'DidUpdate';
+        $auto_notification_map['before_create'] = $class . 'WillCreate';
+        $auto_notification_map['before_store'] = $class . 'WillStore';
+        $auto_notification_map['before_delete'] = $class . 'WillDelete';
+        $auto_notification_map['before_update'] = $class . 'WillUpdate';
+
+        foreach ($auto_notification_map as $cb => $notification) {
+            if (isset($config['notification_map'][$cb])) {
+                if (strpos($config['notification_map'][$cb], $notification) !== false) {
+                    $config['notification_map'][$cb] .= ' ' . $notification;
+                }
+            } else {
+                $config['notification_map'][$cb] = $notification;
+            }
+        }
+
+        if (is_array($config['notification_map'])) {
+            foreach (array_keys($config['notification_map']) as $cb) {
+                $config['registered_callbacks'][$cb][] = 'cbNotificationMapper';
+            }
+        }
+
+        if (!I18N::isEnabled() || empty($config['i18n_fields'])) {
+            $config['i18n_fields'] = [];
+        } elseif (is_string($config['i18n_fields'])) {
+            $i18n_fields = words($config['i18n_fields']);
+            $config['i18n_fields'] = array_combine(
+                $i18n_fields,
+                array_fill(0, count($i18n_fields), true)
+            );
+        } elseif (array_is_list($config['i18n_fields'])) {
+            $config['i18n_fields'] = array_combine(
+                $config['i18n_fields'],
+                array_fill(0, count($config['i18n_fields']), true)
+            );
+        }
+
+        array_unshift($config['registered_callbacks']['after_initialize'], 'cbAfterInitialize');
+
+        $config['known_slots'] = array_merge(
+            array_keys($config['db_fields']),
+            array_keys($config['alias_fields'] ?? []),
+            array_keys($config['additional_fields'] ?? []),
+            array_keys($config['relations'] ?? [])
+        );
+
+        foreach (array_map('strtolower', get_class_methods($class)) as $method) {
+            if (in_array(substr($method, 0, 3), ['get', 'set'])) {
+                $verb = substr($method, 0, 3);
+                $name = substr($method, 3);
+                if (in_array($name, $config['known_slots']) && !in_array($name, static::$reserved_slots) && !isset($config['additional_fields'][$name][$verb])) {
+                    $config['getter_setter_map'][$name][$verb] = $method;
+                }
+            }
+        }
+        self::$config[$class] = $config;
+    }
+
+    /**
+     * fetch config data for the called class
+     *
+     * @param string $key config key
+     * @return mixed value of config key (null if not set)
+     */
+    protected static function config($key)
+    {
+        if (!array_key_exists(static::class, self::$config)) {
+            static::configure();
+        }
+
+        return self::$config[static::class][$key] ?? null;
+    }
+
+    /**
+     * fetch table metadata from db or from local cache
+     *
+     * @param string $db_table
+     * @return bool true if metadata could be fetched
+     */
+    public static function tableScheme($db_table)
+    {
+        if (self::$schemes === null) {
+            $cache = \Studip\Cache\Factory::getCache();
+            self::$schemes = unserialize($cache->read('DB_TABLE_SCHEMES'));
+        }
+        if (!isset(self::$schemes[$db_table])) {
+            $db = DBManager::get()->query("SHOW COLUMNS FROM $db_table");
+            while($rs = $db->fetch(PDO::FETCH_ASSOC)){
+                $db_fields[strtolower($rs['Field'])] = [
+                    'name' => $rs['Field'],
+                    'null' => $rs['Null'],
+                    'default' => $rs['Default'],
+                    'type' => $rs['Type'],
+                    'extra' => $rs['Extra']
+                ];
+                if ($rs['Key'] == 'PRI'){
+                    $pk[] = strtolower($rs['Field']);
+                }
+            }
+            self::$schemes[$db_table]['db_fields'] = $db_fields;
+            self::$schemes[$db_table]['pk'] = $pk;
+            $cache = \Studip\Cache\Factory::getCache();
+            $cache->write('DB_TABLE_SCHEMES', serialize(self::$schemes));
+        }
+        return isset(self::$schemes[$db_table]);
+    }
+
+    /**
+     * force reload of cached table metadata
+     * @return void
+     */
+    public static function expireTableScheme()
+    {
+        \Studip\Cache\Factory::getCache()->expire('DB_TABLE_SCHEMES');
+        self::$schemes = null;
+        self::$config = [];
+    }
+
+    /**
+     * Returns new instance for given key when found in the database, else null.
+     *
+     * @param string|array $id primary key
+     * @return static|null
+     */
+    public static function find($id)
+    {
+        $ref = new ReflectionClass(static::class);
+        /** @var static $record */
+        $record = $ref->newInstanceArgs(func_get_args());
+        if (!$record->isNew()) {
+            return $record;
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * Returns true if given key exists in the database.
+     *
+     * @param string|array $id primary key
+     * @return boolean
+     */
+    public static function exists($id)
+    {
+        $ret = false;
+        $db_table = static::db_table();
+        $record = new static();
+        $record->setId(...func_get_args());
+        $where_query = $record->getWhereQuery();
+        if ($where_query) {
+            $query = "SELECT 1 FROM `$db_table` WHERE "
+                    . join(" AND ", $where_query);
+            $ret = (bool)DBManager::get()->query($query)->fetchColumn();
+        }
+        return $ret;
+    }
+
+    /**
+     * returns number of records
+     *
+     * @param ?string $sql sql clause to use on the right side of WHERE
+     * @param ?array $params params for query
+     * @return int
+     */
+    public static function countBySql($sql = '1', $params = [])
+    {
+        $db_table = static::db_table();
+        $db = DBManager::get();
+        $has_join = stripos($sql, 'JOIN ');
+        if ($has_join === false || $has_join > 10) {
+            $sql = 'WHERE ' . $sql;
+        }
+        $sql = "SELECT count(*) FROM `" .  $db_table . "` " . $sql;
+        $st = $db->prepare($sql);
+        $st->execute($params);
+        return (int)$st->fetchColumn();
+    }
+
+    /**
+     * creates new record with given data in db
+     * returns the new object or null
+     * @param array $data assoc array of record
+     * @return ?static
+     */
+    public static function create($data)
+    {
+        $record = new static();
+        $record->setData($data, false);
+        if ($record->store()) {
+            return $record;
+        } else {
+            return null;
+        }
+    }
+
+    /**
+     * build object with given data
+     *
+     * @param array $data assoc array of record
+     * @param ?bool $is_new set object to new state
+     * @return static
+     */
+    public static function build($data, $is_new = true)
+    {
+        $record = new static();
+        $record->setData($data, !$is_new);
+        $record->setNew($is_new);
+        return $record;
+    }
+
+    /**
+     * build object with given data and mark it as existing
+     *
+     * @param array $data assoc array of record
+     * @return static
+     */
+    public static function buildExisting($data)
+    {
+        return static::build($data, false);
+    }
+
+    /**
+     * generate SimpleORMap object structure from assoc array
+     * if given array contains data of related objects in sub-arrays
+     * they are also generated. Existing records are updated, new records are created
+     * (but changes are not yet stored)
+     *
+     * @param array $data
+     * @return static
+     */
+    public static function import($data)
+    {
+        $record_data = [];
+        $relation_data = [];
+        foreach ($data as $key => $value) {
+            $temp = static::alias_fields()[$key] ?? $key;
+            if (isset(static::db_fields()[$temp])) {
+                $record_data[$key] = $value;
+            } else {
+                $relation_data[$key] = $value;
+            }
+        }
+        $record = static::toObject($record_data);
+        if (!$record instanceof static) {
+            $record = new static();
+            $record->setData($record_data, true);
+        } else {
+            $record->setData($record_data);
+        }
+        foreach ($relation_data as $relation => $data) {
+            if (!$record->isRelation($relation)) {
+                continue;
+            }
+
+            $options = $record->getRelationOptions($relation);
+            if ($options['type'] == 'has_one') {
+                $record->{$relation} = call_user_func([$options['class_name'], 'import'], $data);
+            }
+            if ($options['type'] == 'has_many' || $options['type'] == 'has_and_belongs_to_many') {
+                foreach ($data as $one) {
+                    $current = call_user_func([$options['class_name'], 'import'], $one);
+                    if ($options['type'] == 'has_many') {
+                        $foreign_key_value = call_user_func($options['assoc_func_params_func'], $record);
+                        call_user_func($options['assoc_foreign_key_setter'], $current, $foreign_key_value);
+                    }
+                    if ($current->id !== null) {
+                        $existing = $record->{$relation}->find($current->id);
+                        if ($existing) {
+                            $existing->setData($current);
+                        } else {
+                            $record->{$relation}->append($current);
+                        }
+                    } else {
+                        $record->{$relation}->append($current);
+                    }
+                }
+            }
+        }
+        return $record;
+    }
+
+    /**
+     * returns array of instances of given class filtered by given sql
+     * @param string $sql sql clause to use on the right side of WHERE
+     * @param ?array $params parameters for query
+     * @return static[] array of "self" objects
+     */
+    public static function findBySQL($sql, $params = [])
+    {
+        $db_table = static::db_table();
+
+        $has_join = stripos($sql, 'JOIN ');
+        if ($has_join === false || $has_join > 10) {
+            $sql = 'WHERE ' . $sql;
+        }
+        $sql = "SELECT `" . $db_table . "`.* FROM `" . $db_table . "` " . $sql;
+        $stmt = DBManager::get()->prepare($sql);
+        $stmt->execute($params);
+
+        $record = static::build([], false);
+
+        $ret = [];
+        do  {
+            $clone = clone $record;
+            $clone->setNew(false);
+            $stmt->setFetchMode(PDO::FETCH_INTO, $clone);
+
+            if ($clone = $stmt->fetch()) {
+                $clone->applyCallbacks('after_initialize');
+                $ret[] = $clone;
+            }
+        } while ($clone);
+        return $ret;
+    }
+
+    /**
+     * returns one instance of given class filtered by given sql
+     * only first row of query is used
+     * @param string $where sql clause to use on the right side of WHERE
+     * @param ?array $params parameters for query
+     * @return ?static
+     */
+    public static function findOneBySQL($where, $params = [])
+    {
+        if (stripos($where, 'LIMIT') === false) {
+            $where .= " LIMIT 1";
+        }
+        $found = static::findBySQL($where, $params);
+        return isset($found[0]) ? $found[0] : null;
+    }
+
+    /**
+     * find related records for a n:m relation (has_many_and_belongs_to_many)
+     * using a combination table holding the keys
+     *
+     * @param string $foreign_key_value value of foreign key to find related records
+     * @param array $options relation options from other side of relation
+     * @return static[] array of "self" objects
+     */
+    public static function findThru($foreign_key_value, $options)
+    {
+        $thru_table = $options['thru_table'];
+        $thru_key = $options['thru_key'];
+        $thru_assoc_key = $options['thru_assoc_key'];
+        $assoc_foreign_key = $options['assoc_foreign_key'];
+
+        $db_table = static::db_table();
+
+        $sql = "SELECT `$db_table`.* FROM `$thru_table`
+        INNER JOIN `$db_table` ON `$thru_table`.`$thru_assoc_key` = `$db_table`.`$assoc_foreign_key`
+        WHERE `$thru_table`.`$thru_key` = ? " . ($options['order_by'] ?? '');
+        $st = DBManager::get()->prepare($sql);
+        $st->execute([$foreign_key_value]);
+
+        $record = static::build([], false);
+
+        $ret = [];
+        do {
+            $clone = clone $record;
+            $clone->setNew(false);
+            $st->setFetchMode(PDO::FETCH_INTO, $clone);
+
+            if ($clone = $st->fetch()) {
+                $clone->applyCallbacks('after_initialize');
+                $ret[] = $clone;
+            }
+        } while ($clone);
+        return $ret;
+    }
+
+    /**
+     * passes objects for given sql through given callback
+     *
+     * @param callable $callable callback which gets the current record as param
+     * @param string $sql where clause of sql
+     * @param ?array $params sql statement parameters
+     * @return integer number of found records
+     */
+    public static function findEachBySQL($callable, $sql, $params = [])
+    {
+        $has_join = stripos($sql, 'JOIN ');
+        if ($has_join === false || $has_join > 10) {
+            $sql = "WHERE {$sql}";
+        }
+
+        $db_table = static::db_table();
+        $st = DBManager::get()->prepare("SELECT `{$db_table}`.* FROM `{$db_table}` {$sql}");
+        $st->execute($params);
+
+        // Indicate that we are performing a batch operation
+        static::$performs_batch_operation = true;
+
+        $record = static::build([], false);
+
+        $ret = 0;
+        do {
+            $clone = clone $record;
+            $clone->setNew(false);
+            $st->setFetchMode(PDO::FETCH_INTO, $clone);
+
+            if ($clone = $st->fetch()) {
+                $clone->applyCallbacks('after_initialize');
+                $callable($clone, $ret++);
+            }
+        } while ($clone);
+
+        // Reset batch operation indicator
+        static::$performs_batch_operation = false;
+
+        return $ret;
+    }
+
+    /**
+     * returns array of instances of given class for by given pks
+     * @param ?array $pks array of primary keys
+     * @param ?string $order order by clause
+     * @param ?array $order_params
+     * @return static[]
+     */
+    public static function findMany($pks = [], $order = '', $order_params = [])
+    {
+        $db_table = static::db_table();
+        $pk = static::pk();
+        $db = DBManager::get();
+        if (count($pk) > 1) {
+            throw new Exception('not implemented yet');
+        }
+        $where = "`$db_table`.`{$pk[0]}` IN ("  . $db->quote($pks) . ") ";
+        return static::findBySQL($where . $order, $order_params);
+    }
+
+    /**
+     * passes objects for by given pks through given callback
+     *
+     * @param callable $callable callback which gets the current record as param
+     * @param ?array $pks array of primary keys of called class
+     * @param ?string $order order by sql
+     * @param ?array $order_params
+     * @return integer number of found records
+     */
+    public static function findEachMany($callable, $pks = [], $order = '', $order_params = [])
+    {
+        $db_table = static::db_table();
+        $pk = static::pk();
+        $db = DBManager::get();
+        if (count($pk) > 1) {
+            throw new Exception('not implemented yet');
+        }
+        $where = "`$db_table`.`{$pk[0]}` IN ("  . $db->quote($pks) . ") ";
+        return static::findEachBySQL($callable, $where . $order, $order_params);
+    }
+
+    /**
+     * passes objects for given sql through given callback
+     * and returns an array of callback return values
+     *
+     * @param callable $callable callback which gets the current record as param
+     * @param string $where where clause of sql
+     * @param array $params sql statement parameters
+     * @return array return values of callback
+     */
+    public static function findAndMapBySQL($callable, $where, $params = [])
+    {
+        $ret = [];
+        $calleach = function($m) use (&$ret, $callable) {
+            $ret[] = $callable($m);
+        };
+        static::findEachBySQL($calleach, $where, $params);
+        return $ret;
+    }
+
+    /**
+     * passes objects for by given pks through given callback
+     * and returns an array of callback return values
+     *
+     * @param callable $callable callback which gets the current record as param
+     * @param ?array $pks array of primary keys of called class
+     * @param ?string $order order by sql
+     * @param ?array $order_params
+     * @return array return values of callback
+     */
+    public static function findAndMapMany($callable, $pks = [], $order = '', $order_params = [])
+    {
+        $ret = [];
+        $calleach = function($m) use (&$ret, $callable) {
+            $ret[] = $callable($m);
+        };
+        $db_table = static::db_table();
+        $pk = static::pk();
+        $db = DBManager::get();
+        if (count($pk) > 1) {
+            throw new Exception('not implemented yet');
+        }
+        $where = "`$db_table`.`{$pk[0]}` IN ("  . $db->quote($pks) . ") ";
+        static::findEachBySQL($calleach, $where . $order, $order_params);
+        return $ret;
+    }
+
+    /**
+     * deletes objects specified by sql clause
+     * @param string $where sql clause to use on the right side of WHERE
+     * @param ?array $params parameters for query
+     * @return integer number of deleted records
+     */
+    public static function deleteBySQL($where, $params = [])
+    {
+        $killeach = function($record) {$record->delete();};
+        return static::findEachBySQL($killeach, $where, $params);
+    }
+
+    /**
+     * returns object of given class for given id or null
+     * the param could be a string, an assoc array containing primary key field
+     * or an already matching object. In all these cases an object is returned
+     *
+     * @param string|static|array $id_or_object id as string, object or assoc array
+     * @return static
+     */
+    public static function toObject($id_or_object)
+    {
+        if ($id_or_object instanceof static) {
+            return $id_or_object;
+        }
+        if (is_array($id_or_object)) {
+            $pk = static::pk();
+            $key_values = [];
+            foreach ($pk as $key) {
+                if (array_key_exists($key, $id_or_object)) {
+                    $key_values[] = $id_or_object[$key];
+                }
+            }
+            if (count($pk) === count($key_values)) {
+                if (count($pk) === 1) {
+                    $id = $key_values[0];
+                } else {
+                    $id = $key_values;
+                }
+            } else {
+                $id = null;
+            }
+        } else {
+            $id = $id_or_object;
+        }
+        return static::find($id);
+    }
+
+    /**
+     * interceptor for static findByColumn / findEachByColumn / countByColumn /
+     * deleteByColumn magic
+     *
+     * @param string $name
+     * @param array $arguments
+     * @throws BadMethodCallException
+     * @return int|static|static[]
+     */
+    public static function __callStatic(string $name, array $arguments)
+    {
+        $db_table = static::db_table();
+        $alias_fields = static::alias_fields();
+        $db_fields = static::db_fields();
+        $name = strtolower($name);
+        $order = '';
+        $param_arr = [];
+        $where = '';
+        $where_param = is_array($arguments[0]) ? $arguments[0] : [$arguments[0]];
+        $action = strstr($name, 'by', true);
+        $field = substr($name, strlen($action) + 2);
+        switch ($action) {
+            case 'findone':
+                $order = $arguments[1] ?? '';
+                $param_arr[0] =& $where;
+                $param_arr[1] = [$where_param];
+                $method = 'findonebysql';
+                break;
+            case 'find':
+            case 'findmany':
+                $order = $arguments[1] ?? '';
+                $param_arr[0] =& $where;
+                $param_arr[1] = [$where_param];
+                $method = 'findbysql';
+                break;
+            case 'findeach':
+            case 'findeachmany':
+                $order = $arguments[2] ?? '';
+                $param_arr[0] = $arguments[0];
+                $param_arr[1] =& $where;
+                $param_arr[2] = [$arguments[1]];
+                $method = 'findeachbysql';
+                break;
+            case 'count':
+            case 'delete':
+                $param_arr[0] =& $where;
+                $param_arr[1] = [$where_param];
+                $method = "{$action}bysql";
+                break;
+            default:
+                throw new BadMethodCallException("Method " . static::class . "::$name not found");
+        }
+        if (isset($alias_fields[$field])) {
+            $field = $alias_fields[$field];
+        }
+        if (isset($db_fields[$field])) {
+            $where = "`$db_table`.`$field` IN(?) " . $order;
+            return call_user_func_array([static::class, $method], $param_arr);
+        }
+        throw new BadMethodCallException("Method " . static::class . "::$name not found");
+    }
+
+    /**
+     * constructor, give primary key of record as param to fetch
+     * corresponding record from db if available, if not preset primary key
+     * with given value. Give null to create new record
+     *
+     * @param null|int|string|array $id primary key of table
+     */
+    function __construct($id = null)
+    {
+        foreach(['has_many', 'belongs_to', 'has_one', 'has_and_belongs_to_many'] as $type) {
+            foreach (array_keys($this->$type()) as $one) {
+                $this->relations[$one] = null;
+            }
+        }
+
+        if ($id) {
+            $this->setId($id);
+        }
+        $this->restore();
+    }
+
+    /**
+     * returns internal used id value (multiple keys concatenated with _)
+     * @param mixed $field unused parameter
+     * @return ?string
+     */
+    protected function _getId($field)
+    {
+        return is_null($this->getId())
+             ? null
+             : implode(self::ID_SEPARATOR, $this->getId());
+    }
+
+    /**
+     * sets internal used id value (multiple keys concatenated with _)
+     * @param string $field Field to set (unused since it's always the id)
+     * @param string $value Value for id field
+     * @return bool
+     */
+    protected function _setId($field, $value)
+    {
+        return $this->setId(explode(self::ID_SEPARATOR, $value));
+    }
+
+    /**
+     * retrieves an additional field value from relation
+     *
+     * @param string $field
+     * @return mixed
+     */
+    protected function _getAdditionalValueFromRelation($field)
+    {
+        [$relation, $relation_field] = [$this->additional_fields()[$field]['relation'],
+                                                $this->additional_fields()[$field]['relation_field']];
+        if (!array_key_exists($field, $this->additional_data)) {
+            $this->_setAdditionalValue($field, $this->getRelationValue($relation, $relation_field));
+        }
+        return $this->additional_data[$field];
+    }
+
+    /**
+     * sets additional value in field imported from relation
+     *
+     * @param string $field
+     * @param mixed $value
+     * @return mixed
+     */
+    protected function _setAdditionalValueFromRelation($field, $value)
+    {
+        [$relation, $relation_field] = [$this->additional_fields()[$field]['relation'],
+                $this->additional_fields()[$field]['relation_field']];
+        $this->$relation->$field = $value;
+        unset($this->additional_data[$field]);
+        return $this->_getAdditionalValueFromRelation($field);
+    }
+
+    /**
+     * @param string $field
+     * @return mixed
+     */
+    protected function _getAdditionalValue($field)
+    {
+        return $this->additional_data[$field];
+    }
+
+    /**
+     * @param string $field
+     * @param mixed $value
+     * @return mixed
+     */
+    protected function _setAdditionalValue($field, $value)
+    {
+        return $this->additional_data[$field] = $value;
+    }
+
+    /**
+     * clean up references after cloning
+     * @return void
+     */
+    function __clone()
+    {
+        $this->setNew(true);
+        //all references link still to old object => reset all aliases
+        foreach ($this->alias_fields() as $alias => $field) {
+            if (isset($this->db_fields()[$field])) {
+                $content_value = $this->content[$field];
+                $content_db_value = $this->content_db[$field];
+                unset($this->content[$alias]);
+                unset($this->content_db[$alias]);
+                unset($this->content[$field]);
+                unset($this->content_db[$field]);
+                if (is_object($content_value)) {
+                    $this->content[$field] = clone $content_value;
+                } else {
+                    $this->content[$field] = $content_value;
+                }
+                if (is_object($content_db_value)) {
+                    $this->content_db[$field] = clone $content_db_value;
+                } else {
+                    $this->content_db[$field] = $content_db_value;
+                }
+            }
+        }
+        foreach ($this->alias_fields() as $alias => $field) {
+            if (isset($this->db_fields()[$field])) {
+                $this->content[$alias] =& $this->content[$field];
+                $this->content_db[$alias] =& $this->content_db[$field];
+            }
+        }
+        //unset all relations for now
+        //TODO: maybe a deep copy of all belonging objects is more appropriate
+        foreach(['has_many', 'belongs_to', 'has_one', 'has_and_belongs_to_many'] as $type) {
+            foreach (array_keys($this->$type()) as $one) {
+                $this->relations[$one] = null;
+            }
+        }
+        //begun the clone war has... hmpf
+    }
+
+    /**
+     * try to determine all needed options for a relationship from
+     * configured options
+     *
+     * @param string $type
+     * @param string $name
+     * @param array $options
+     * @throws Exception if options for thru_table could not be determined
+     * @return array
+     */
+    protected function parseRelationOptions($type, $name, $options)
+    {
+        if (empty($options['class_name'])) {
+            throw new Exception('Option class_name not set for relation ' . $name);
+        }
+        if (empty($options['assoc_foreign_key'])) {
+            if ($type === 'has_many' || $type === 'has_one') {
+                $options['assoc_foreign_key'] = $this->pk()[0];
+            } else if ($type === 'belongs_to') {
+                $options['assoc_foreign_key'] = 'id';
+            }
+        }
+        if ($type === 'has_and_belongs_to_many') {
+            $thru_table = $options['thru_table'];
+            if (empty($options['thru_key'])) {
+                $options['thru_key'] = $this->pk()[0];
+            }
+            if (empty($options['thru_assoc_key']) || empty($options['assoc_foreign_key'])) {
+                $class = $options['class_name'];
+                $record = new $class();
+                $meta = $record->getTableMetadata();
+                if (empty($options['thru_assoc_key'])) {
+                    $options['thru_assoc_key'] = $meta['pk'][0];
+                }
+                if (empty($options['assoc_foreign_key'])) {
+                    $options['assoc_foreign_key']= $meta['pk'][0];
+                }
+            }
+            static::tableScheme($thru_table);
+            if (is_array(self::$schemes[$thru_table])) {
+                $thru_key_ok = isset(self::$schemes[$thru_table]['db_fields'][$options['thru_key']]);
+                $thru_assoc_key_ok = isset(self::$schemes[$thru_table]['db_fields'][$options['thru_assoc_key']]);
+            }
+            if (!$thru_assoc_key_ok || !$thru_key_ok) {
+                throw new Exception("Could not determine keys for relation " . $name . " through table " . $thru_table);
+            }
+            if ($options['assoc_foreign_key'] instanceof Closure) {
+                throw new Exception("For relation " . $name . " assoc_foreign_key must be a name of a column");
+            }
+        }
+        if (empty($options['assoc_func'])) {
+            if ($type !== 'has_and_belongs_to_many') {
+                $options['assoc_func'] = $options['assoc_foreign_key'] === 'id' ? 'find' : 'findBy' . $options['assoc_foreign_key'];
+            } else {
+                $options['assoc_func'] = 'findThru';
+            }
+        }
+        if (empty($options['foreign_key'])) {
+            $options['foreign_key'] = 'id';
+        }
+        if (isset($options['foreign_key']) && $options['foreign_key'] instanceof Closure) {
+            $options['assoc_func_params_func'] = function($record) use ($name, $options) { return call_user_func($options['foreign_key'], $record, $name, $options);};
+        } else {
+            $options['assoc_func_params_func'] = function($record) use ($name, $options) { return $options['foreign_key'] === 'id' ? $record->getId() : $record->getValue($options['foreign_key']);};
+        }
+        if (isset($options['assoc_foreign_key']) && $options['assoc_foreign_key'] instanceof Closure) {
+            if ($type === 'belongs_to') {
+                $options['assoc_foreign_key_getter'] = function($record, $that) use ($name, $options) { return call_user_func($options['assoc_foreign_key'], $record, $name, $options, $that);};
+            } else {
+                $options['assoc_foreign_key_setter'] = function($record, $params) use ($name, $options) { return call_user_func($options['assoc_foreign_key'], $record, $params, $name, $options);};
+            }
+        } elseif (!empty($options['assoc_foreign_key'])) {
+            if ($type === 'belongs_to') {
+                $options['assoc_foreign_key_getter'] = function($record, $that) use ($name, $options) { return $record->getValue($options['assoc_foreign_key']);};
+            } else {
+                $options['assoc_foreign_key_setter'] = function($record, $value) use ($name, $options) { return $record->setValue($options['assoc_foreign_key'], $value);};
+            }
+        } else {
+            throw new Exception("Could not determine assoc_foreign_key for relation " . $name);
+        }
+        return $options;
+    }
+
+    /**
+     * returns array with option for given relation
+     * available options:
+     * 'type':                   relation type, on of 'has_many', 'belongs_to', 'has_one', 'has_and_belongs_to_many'
+     * 'class_name':             name of class for related records
+     * 'foreign_key':            name of column with foreign key
+     *                           or callback to retrieve foreign key value
+     * 'assoc_foreign_key':      name of foreign key column in related class
+     * 'assoc_func':             name of static method to call on related class to find related records
+     * 'assoc_func_params_func': callback to retrieve params for assoc_func
+     * 'thru_table':             name of relation table for n:m relation
+     * 'thru_key':               name of column holding foreign key in relation table
+     * 'thru_assoc_key':         name of column holding foreign key from related class in relation table
+     * 'on_delete':              contains simply 'delete' to indicate that related records should be deleted
+     *                           or callback to invoke before record gets deleted
+     * 'on_store':               contains simply 'store' to indicate that related records should be stored
+     *                           or callback to invoke after record gets stored
+     *
+     * @param string $relation name of relation
+     * @return array assoc array containing options
+     */
+    function getRelationOptions($relation)
+    {
+        $options = [];
+        foreach(['has_many', 'belongs_to', 'has_one', 'has_and_belongs_to_many'] as $type) {
+            if (isset($this->$type()[$relation])) {
+                $options = self::$config[get_class($this)][$type][$relation];
+                if (!isset($options['type'])) {
+                    $options = $this->parseRelationOptions($type, $relation, $options, $this->db_table());
+                    $options['type'] = $type;
+                    self::$config[get_class($this)][$type][$relation] = $options;
+                }
+                break;
+            }
+        }
+        return $options;
+    }
+
+    /**
+     * returns table and columns metadata
+     *
+     * @return array assoc array with columns, primary keys and name of table
+     */
+    function getTableMetadata()
+    {
+        return ['fields' => $this->db_fields(),
+                     'pk' => $this->pk(),
+                     'table' => $this->db_table(),
+                     'additional_fields' => $this->additional_fields(),
+                     'alias_fields' => $this->alias_fields(),
+                     'relations' => array_keys($this->relations)];
+    }
+
+    /**
+     * returns true, if table has an auto_increment column
+     *
+     * @return boolean
+     */
+    function hasAutoIncrementColumn()
+    {
+        return $this->db_fields()[$this->pk()[0]]['extra'] == 'auto_increment';
+    }
+
+    /**
+     * set primary key for entry, combined keys must be passed as array
+     * @param int|string|array $id primary key
+     * @throws InvalidArgumentException if given key is not complete
+     * @return boolean
+     */
+    public function setId($id)
+    {
+        if (!is_array($id)){
+            $id = [$id];
+        }
+        if (count($this->pk()) != count($id)){
+            throw new InvalidArgumentException("Invalid ID, Primary Key {$this->db_table()} is " .join(",",$this->pk()));
+        } else {
+            foreach ($this->pk() as $count => $key){
+                $this->content[$key] = $id[$count];
+            }
+            return true;
+        }
+    }
+
+    /**
+     * returns primary key, multiple keys as array
+     * @return null|string|array current primary key, null if not set
+     */
+    function getId()
+    {
+        if (count($this->pk()) == 1) {
+            return $this->content[$this->pk()[0]] ?? null;
+        } else {
+            $id = [];
+            foreach ($this->pk() as $key) {
+                if (array_key_exists($key, $this->content)) {
+                    $id[] = $this->content[$key];
+                }
+            }
+            return (count($this->pk()) == count($id) ? $id : null);
+        }
+    }
+
+    /**
+     * create new unique pk as md5 hash
+     * if pk consists of multiple columns, false is returned
+     * @return boolean|string
+     */
+    function getNewId()
+    {
+        $id = false;
+        if (count($this->pk()) == 1) {
+            do {
+                $id = md5(uniqid($this->db_table(), 1));
+                $db = DBManager::get()->query("SELECT `{$this->pk()[0]}` FROM `{$this->db_table()}` "
+                . "WHERE `{$this->pk()[0]}` = '$id'");
+            } while($db->fetch());
+        }
+        return $id;
+    }
+
+    /**
+     * returns data of table row as assoc array
+     * pass array of fieldnames or ws separated string to limit
+     * fields
+     *
+     * @param null|array|string $only_these_fields limit returned fields
+     * @return array
+     */
+    function toArray($only_these_fields = null)
+    {
+        $ret = [];
+        if (is_string($only_these_fields)) {
+            $only_these_fields = words($only_these_fields);
+        }
+        $fields = array_diff($this->known_slots(), array_keys($this->relations));
+        if (is_array($only_these_fields)) {
+            $only_these_fields = array_filter(array_map(function($s) {
+                return is_string($s) ? strtolower($s) : null;
+            }, $only_these_fields));
+            $fields = array_intersect($only_these_fields, $fields);
+        }
+        foreach ($fields as $field) {
+            $ret[$field] = $this->getValue($field);
+            if ($ret[$field] instanceof StudipArrayObject) {
+                $ret[$field] = $ret[$field]->getArrayCopy();
+            }
+        }
+        return $ret;
+    }
+
+    /**
+     * Returns data of table row as assoc array with raw contents like
+     * they are in the database.
+     * Pass array of fieldnames or ws separated string to limit
+     * fields.
+     *
+     * @param null|array|string $only_these_fields
+     * @return array
+     */
+    function toRawArray($only_these_fields = null)
+    {
+        $ret = [];
+        if (is_string($only_these_fields)) {
+            $only_these_fields = words($only_these_fields);
+        }
+        $fields = array_keys($this->db_fields());
+        if (is_array($only_these_fields)) {
+            $only_these_fields = array_filter(array_map(function ($s) {
+                return is_string($s) ? strtolower($s) : null;
+            }, $only_these_fields));
+            $fields = array_intersect($only_these_fields, $fields);
+        }
+        foreach ($fields as $field) {
+            if ($this->content[$field] instanceof I18NString) {
+                $ret[$field] = $this->content[$field]->original();
+            } elseif ($this->content[$field] === null) {
+                $ret[$field] = null;
+            } else {
+                $ret[$field] = (string)$this->content[$field];
+            }
+        }
+        return $ret;
+    }
+
+    /**
+     * returns data of table row as assoc array
+     * including related records with a 'has*' relationship
+     * recurses one level without param
+     *
+     * $only_these_fields limits output for relationships in this way:
+     * $only_these_fields = array('field_1',
+     *                            'field_2',
+     *                            'relation1',
+     *                            'relation2' => array('rel2_f1',
+     *                                                 'rel2_f2',
+     *                                                 'rel2_rel11' => array(
+     *                                                           rel2_rel1_f1)
+     *                                                )
+     *                           )
+     * Here all fields of relation1 will be returned.
+     *
+     * @param null|array|string $only_these_fields limit returned fields
+     * @return array
+     */
+    function toArrayRecursive($only_these_fields = null)
+    {
+        if (is_string($only_these_fields)) {
+            $only_these_fields = words($only_these_fields);
+        }
+        if (is_null($only_these_fields)) {
+            $only_these_fields = $this->known_slots();
+        }
+        $ret = $this->toArray($only_these_fields);
+        $relations = [];
+        if (is_array($only_these_fields)) {
+            foreach ($only_these_fields as $key => $value) {
+                if (!is_array($value) &&
+                    array_key_exists(strtolower($value), $this->relations)
+                ) {
+                    $relations[strtolower($value)] = 0; //not null|array|string to stop recursion
+                }
+                if (array_key_exists(strtolower($key), $this->relations)) {
+                    $relations[strtolower($key)] = $value;
+                }
+            }
+        }
+        if (count($relations)) {
+            foreach ($relations as $relation_name => $relation_only_these_fields) {
+                $options = $this->getRelationOptions($relation_name);
+                if ($options['type'] === 'has_one' ||
+                        $options['type'] === 'belongs_to') {
+                    $ret[$relation_name] =
+                            $this->{$relation_name}->
+                                            toArrayRecursive($relation_only_these_fields);
+                }
+                if ($options['type'] === 'has_many' ||
+                    $options['type'] === 'has_and_belongs_to_many') {
+                    $ret[$relation_name] =
+                            $this->{$relation_name}->
+                                            sendMessage('toArrayRecursive',
+                                            [$relation_only_these_fields]);
+                }
+            }
+        }
+        return $ret;
+    }
+
+    /**
+     * returns value of a column
+     *
+     * @throws InvalidArgumentException if column could not be found
+     * @throws BadMethodCallException if getter for additional field could not be found
+     * @param string $field
+     * @return null|string|SimpleORMapCollection
+     */
+    public function getValue($field)
+    {
+        $field = strtolower($field);
+
+        // No value defined, throw exception
+        if (!in_array($field, $this->known_slots())) {
+            throw new InvalidArgumentException(static::class . '::'.$field . ' not found.');
+        }
+
+        // Get value by getter
+        if (isset($this->getter_setter_map()[$field]['get'])) {
+            return call_user_func([$this, $this->getter_setter_map()[$field]['get']]);
+        }
+
+        // Get value from content
+        if (array_key_exists($field, $this->content)) {
+            return $this->content[$field];
+        }
+
+        // Get value from relation
+        if (array_key_exists($field, $this->relations)) {
+            $this->initRelation($field);
+            return $this->relations[$field];
+        }
+
+        // Get value from additional_field
+        if (isset($this->additional_fields()[$field]['get'])) {
+            // Getter is defined as a closure
+            if ($this->additional_fields()[$field]['get'] instanceof Closure) {
+                return call_user_func_array($this->additional_fields()[$field]['get'], [$this, $field]);
+            }
+
+            // Getter is defined as a method of this object
+            return call_user_func([$this, $this->additional_fields()[$field]['get']], $field);
+        }
+
+        // No value found, throw exception
+        throw new RuntimeException('No value could be found for ' . static::class . '::' . $field);
+    }
+
+    /**
+     * gets a value from a related object
+     * only possible, if the relation has cardinality 1
+     * e.g. 'has_one' or 'belongs_to'
+     *
+     * @param string $relation name of relation
+     * @param string $field name of column
+     * @throws InvalidArgumentException if no relation with given name is found
+     * @return mixed the value from the related object
+     */
+    function getRelationValue($relation, $field)
+    {
+        $field = strtolower($field);
+        $options = $this->getRelationOptions($relation);
+        if ($options['type'] === 'has_one' || $options['type'] === 'belongs_to') {
+            return $this->{$relation}->{$field} ?? null;
+        } else {
+            throw new InvalidArgumentException('Relation ' . $relation . ' not found or not applicable.');
+        }
+    }
+
+    /**
+     * returns default value for column
+     *
+     * @param string $field name of column
+     * @return mixed the default value
+     */
+     function getDefaultValue($field)
+     {
+         $default_value = null;
+         if (!isset($this->default_values()[$field])) {
+             if (!in_array($field, $this->pk())) {
+                 $meta = $this->db_fields()[$field];
+                 if (isset($meta['default'])) {
+                     $default_value = $meta['default'];
+                 } elseif ($meta['null'] == 'NO') {
+                     if (strpos($meta['type'], 'text') !== false || strpos($meta['type'], 'char') !== false) {
+                         $default_value = '';
+                     }
+                     if (strpos($meta['type'], 'int') !== false) {
+                         $default_value = '0';
+                     }
+                 }
+             }
+         } else {
+             $default_value = $this->default_values()[$field];
+         }
+         return $default_value;
+     }
+
+    /**
+     * sets value of a column
+     *
+     * @throws InvalidArgumentException if column could not be found
+     * @throws BadMethodCallException if setter for additional field could not be found
+     * @param string $field
+     * @param mixed $value
+     * @return string
+     */
+     function setValue($field, $value)
+     {
+         $field = strtolower($field);
+         $ret = false;
+         if (in_array($field, $this->known_slots())) {
+             if (isset($this->getter_setter_map()[$field]['set'])) {
+                 return call_user_func([$this, $this->getter_setter_map()[$field]['set']], $value);
+             }
+             if (array_key_exists($field, $this->content)) {
+                 if (array_key_exists($field, $this->serialized_fields())) {
+                     $ret = $this->setSerializedValue($field, $value);
+                 } elseif ($this->isI18nField($field)) {
+                         $ret = $this->setI18nValue($field, $value);
+                 } else {
+                     $ret = ($this->content[$field] = $value);
+                 }
+             } elseif (isset($this->additional_fields()[$field]['set'])) {
+                 if ($this->additional_fields()[$field]['set'] instanceof Closure) {
+                     return call_user_func_array($this->additional_fields()[$field]['set'], [$this, $field, $value]);
+                 } else {
+                     return call_user_func([$this, $this->additional_fields()[$field]['set']], $field, $value);
+                 }
+             } elseif (array_key_exists($field, $this->relations)) {
+                 $options = $this->getRelationOptions($field);
+                 if ($options['type'] === 'has_one' || $options['type'] === 'belongs_to') {
+                     if (is_a($value, $options['class_name'])) {
+                         $this->relations[$field] = $value;
+                         if ($options['type'] == 'has_one') {
+                             $foreign_key_value = call_user_func($options['assoc_func_params_func'], $this);
+                             call_user_func($options['assoc_foreign_key_setter'], $value, $foreign_key_value);
+                         } else {
+                             $assoc_foreign_key_value = call_user_func($options['assoc_foreign_key_getter'], $value, $this);
+                             if ($assoc_foreign_key_value === null) {
+                                 throw new InvalidArgumentException(sprintf('trying to set belongs_to object of type: %s, but assoc_foreign_key: %s is null', get_class($value), $options['assoc_foreign_key']));
+                             }
+                             $this->setValue($options['foreign_key'], $assoc_foreign_key_value);
+                         }
+                     } elseif (
+                         $value === null
+                         && $this->db_fields()[$options['foreign_key']]['null'] === 'YES'
+                     ) {
+                         $this->resetRelation($field);
+                         $this->setValue($options['foreign_key'], null);
+
+                     } else {
+                         throw new InvalidArgumentException(sprintf('relation %s expects object of type: %s', $field, $options['class_name']));
+                     }
+                 }
+                 if ($options['type'] == 'has_many' || $options['type'] == 'has_and_belongs_to_many') {
+                     if (is_array($value) || $value instanceof Traversable) {
+                         $new_ids = [];
+                         $old_ids = $this->{$field}->pluck('id');
+                         foreach ($value as $current) {
+                             if (!is_a($current, $options['class_name'])) {
+                                 throw new InvalidArgumentException(sprintf('relation %s expects object of type: %s', $field, $options['class_name']));
+                             }
+                             if ($options['type'] == 'has_many') {
+                                 $foreign_key_value = call_user_func($options['assoc_func_params_func'], $this);
+                                 call_user_func($options['assoc_foreign_key_setter'], $current, $foreign_key_value);
+                             }
+                             if ($current->id !== null) {
+                                 $new_ids[] = $current->id;
+                                 $existing = $this->{$field}->find($current->id);
+                                 if ($existing) {
+                                     $existing->setData($current);
+                                 } else {
+                                     $this->{$field}->append($current);
+                                 }
+                             } else {
+                                 $this->{$field}->append($current);
+                             }
+                         }
+                         foreach (array_diff($old_ids, $new_ids) as $to_delete) {
+                             $this->{$field}->unsetByPK($to_delete);
+                         }
+                     } else {
+                         throw new InvalidArgumentException(sprintf('relation %s expects collection or array of objects of type: %s', $field, $options['class_name']));
+                     }
+                 }
+             }
+         } else {
+             throw new InvalidArgumentException(get_class($this) . '::'. $field . ' not found.');
+         }
+         return $ret;
+     }
+
+    /**
+     * magic method for dynamic properties
+     *
+     * @throws InvalidArgumentException if column could not be found
+     * @throws BadMethodCallException if getter for additional field could not be found
+     * @param string $field the column or additional field
+     * @return null|string|SimpleORMapCollection
+     */
+    function __get($field)
+    {
+        return $this->getValue($field);
+    }
+    /**
+     * magic method for dynamic properties
+     *
+     * @throws InvalidArgumentException if column could not be found
+     * @throws BadMethodCallException if setter for additional field could not be found
+     * @param string $field
+     * @param string $value
+     * @return string
+     */
+    function __set($field, $value)
+    {
+        return $this->setValue($field, $value);
+    }
+    /**
+     * magic method for dynamic properties
+     *
+     * @param string $field
+     * @return bool
+     */
+    function __isset($field)
+    {
+        $field = strtolower($field);
+        if (in_array($field, $this->known_slots())) {
+            $value = $this->getValue($field);
+            return $value instanceOf SimpleORMapCollection ? (bool)count($value) : !is_null($value);
+        } else {
+            return false;
+        }
+    }
+
+    /**
+     * ArrayAccess: Check whether the given offset exists.
+     *
+     * @param string $offset
+     */
+    public function offsetExists($offset): bool
+    {
+        return $this->__isset($offset);
+    }
+
+    /**
+     * ArrayAccess: Get the value at the given offset.
+     *
+     * @throws InvalidArgumentException if column could not be found
+     * @throws BadMethodCallException if getter for additional field could not be found
+     * @param string $offset the column or additional field
+     * @return null|string|SimpleORMapCollection
+     */
+    public function offsetGet($offset): mixed
+    {
+        return $this->getValue($offset);
+    }
+
+    /**
+     * ArrayAccess: Set the value at the given offset.
+     *
+     * @throws InvalidArgumentException if column could not be found
+     * @throws BadMethodCallException if setter for additional field could not be found
+     * @param string $offset
+     * @param mixed $value
+     */
+    public function offsetSet($offset, $value): void
+    {
+        $this->setValue($offset, $value);
+    }
+
+    /**
+     * ArrayAccess: unset the value at the given offset (not applicable)
+     *
+     * @param string $offset
+     */
+    public function offsetUnset($offset): void
+    {
+
+    }
+
+    /**
+     * IteratorAggregate
+     */
+    public function getIterator(): ArrayIterator
+    {
+        return new ArrayIterator($this->toArray());
+    }
+
+    /**
+     * Countable
+     */
+    public function count(): int
+    {
+        return count($this->known_slots()) - count($this->relations);
+    }
+
+    /**
+     * check if given column exists in table
+     * @param string $field
+     * @return boolean
+     */
+    function isField($field)
+    {
+        $field = strtolower($field);
+        return isset($this->db_fields()[$field]);
+    }
+
+    /**
+     * check if given relation exists in this class
+     * @param string $field
+     * @return boolean
+     */
+    function isRelation($field)
+    {
+        $field = strtolower($field);
+        return array_key_exists($field, $this->relations);
+    }
+
+    /**
+     * check if given column is additional
+     * @param string $field
+     * @return boolean
+     */
+    function isAdditionalField($field)
+    {
+        $field = strtolower($field);
+        return isset($this->additional_fields()[$field]);
+    }
+
+    /**
+     * check if given column is an alias
+     * @param string $field
+     * @return boolean
+     */
+    function isAliasField($field)
+    {
+        $field = strtolower($field);
+        return isset($this->alias_fields()[$field]);
+    }
+
+    /**
+     * check if given column is a multi-language field
+     * @param string $field
+     * @return boolean
+     */
+    function isI18nField($field)
+    {
+        $field = strtolower($field);
+        return isset($this->i18n_fields()[$field]);
+    }
+
+    /**
+     * set multiple column values
+     * if second param is set, existing data in object will be
+     * discarded and dirty state is cleared,
+     * else new data overrides old data
+     *
+     * @param ?iterable $data assoc array
+     * @param ?boolean $reset existing data in object will be discarded
+     * @return int|bool number of columns changed
+     */
+    function setData($data, $reset = false)
+    {
+        $count = 0;
+        if ($reset) {
+            if ($this->applyCallbacks('before_initialize') === false) {
+                return false;
+            }
+            $this->initializeContent();
+        }
+        if (is_iterable($data)) {
+            foreach($data as $key => $value) {
+                $key = strtolower($key);
+                if (isset($this->db_fields()[$key])
+                    || isset($this->alias_fields()[$key])
+                    || isset($this->additional_fields()[$key]['set'])
+                ) {
+                    $this->setValue($key, $value);
+                    ++$count;
+                }
+            }
+        }
+        if ($reset) {
+            $this->applyCallbacks('after_initialize');
+        }
+        return $count;
+    }
+
+    /**
+     * check if object exists in database
+     * @return boolean
+     */
+    function isNew()
+    {
+        return $this->is_new;
+    }
+
+    /**
+     * check if object was deleted
+     *
+     * @return boolean
+     */
+    function isDeleted()
+    {
+        return $this->is_deleted;
+    }
+
+    /**
+     * set object to new state
+     * @param boolean $is_new
+     * @return boolean
+     */
+    function setNew($is_new)
+    {
+        return $this->is_new = $is_new;
+    }
+
+    /**
+     * returns sql clause with current table and pk
+     * @throws UnexpectedValueException if the primary key is incomplete
+     * @return boolean|array<string>
+     */
+    function getWhereQuery()
+    {
+        $where_query = null;
+        $pk_not_set = [];
+        foreach ($this->pk() as $key) {
+            $pk = $this->content_db[$key] ?? $this->content[$key] ?? null;
+            if (isset($pk)) {
+                $where_query[] = "`{$this->db_table()}`.`{$key}` = "  . DBManager::get()->quote($pk);
+            } else {
+                $pk_not_set[] = $key;
+            }
+        }
+        if (!$where_query || count($pk_not_set)){
+            if ($this->isNew()) {
+                return false;
+            } else {
+                throw new UnexpectedValueException(sprintf("primary key incomplete: %s must not be null", join(',',$pk_not_set)));
+            }
+        }
+        return $where_query;
+    }
+
+    /**
+     * restore entry from database
+     * @return boolean
+     */
+    function restore()
+    {
+        $where_query = $this->getWhereQuery();
+        $id = $this->getId();
+        if ($where_query) {
+            if ($this->applyCallbacks('before_initialize') === false) {
+                return false;
+            }
+            $this->initializeContent();
+            $query = "SELECT * FROM `{$this->db_table()}` WHERE "
+                    . join(" AND ", $where_query);
+            $st = DBManager::get()->prepare($query);
+            $st->execute();
+            $st->setFetchMode(PDO::FETCH_INTO , $this);
+            if ($st->fetch()) {
+                $this->setNew(false);
+                $this->applyCallbacks('after_initialize');
+                return true;
+            }
+        }
+        $this->setData([], true);
+        $this->setNew(true);
+        if (isset($id)) {
+            $this->setId($id);
+        }
+        return false;
+    }
+
+    /**
+     * store entry in database
+     *
+     * @throws UnexpectedValueException if there are forbidden NULL values
+     * @return number|boolean
+     */
+    function store()
+    {
+        // Set id or prepare setting of id
+        if ($this->isNew() && $this->getId() === null) {
+            // Explicitly set id to 0 if auto increment pk is null
+            if ($this->hasAutoIncrementColumn()) {
+                $this->setId(0);
+            } else {
+                $this->setId($this->getNewId());
+            }
+        }
+
+        if ($this->applyCallbacks('before_store') === false) {
+            return false;
+        }
+
+        $ret = 0;
+
+        if (!$this->isDeleted() && ($this->isDirty() || $this->isNew())) {
+            $callback = $this->isNew() ? 'before_create' : 'before_update';
+            if ($this->applyCallbacks($callback) === false) {
+                return false;
+            }
+
+            // Collect i18n contents
+            $i18ncontent = [];
+            foreach (array_keys($this->i18n_fields()) as $field) {
+                if ($this->content[$field] instanceof I18NString) {
+                    $i18ncontent[$field] = $this->content[$field];
+                    $this->content[$field] = $this->content[$field]->original();
+                    $this->content_db[$field] = $this->content_db[$field]->original();
+                }
+            }
+
+            // Create sql data assignment chunks
+            foreach ($this->db_fields() as $field => $meta) {
+                $value = $this->content[$field];
+                if ($field == 'chdate' && !$this->isFieldDirty($field) && $this->isDirty()) {
+                    $value = time();
+                }
+                if ($field == 'mkdate') {
+                    if ($this->isNew()) {
+                        if (!$this->isFieldDirty($field)) {
+                            $value = time();
+                        }
+                    } else {
+                        continue;
+                    }
+                }
+                if ($value === null && $meta['null'] == 'NO') {
+                    throw new UnexpectedValueException($this->db_table() . '.' . $field . ' must not be null.');
+                }
+                if (is_float($value)) {
+                    $value = str_replace(',', '.', $value);
+                }
+                $this->content[$field] = $value;
+                $query_part[] = "`$field` = " . DBManager::get()->quote($value) . " ";
+            }
+
+            // Create store query
+            if (!$this->isNew()) {
+                $where_query = $this->getWhereQuery();
+                $query = "UPDATE `{$this->db_table()}` SET "
+                    . implode(',', $query_part);
+                $query .= " WHERE " . join(" AND ", $where_query);
+            } else {
+                $query = "INSERT INTO `{$this->db_table()}` SET "
+                    . implode(',', $query_part);
+            }
+            $ret = DBManager::get()->exec($query);
+
+            // Retrieve generated id from database if pk is an auto increment
+            // column
+            if ($this->isNew()) {
+                if ($this->hasAutoIncrementColumn() && !$this->getId()) {
+                    $this->setId(DBManager::get()->lastInsertId());
+                }
+            }
+
+            // Store i18n contents
+            foreach ($i18ncontent as $field => $one) {
+                $meta = [
+                    'object_id' => $this->getId(),
+                    'table'     => $this->db_table(),
+                    'field'     => $field
+                ];
+                $one->setMetadata($meta);
+                $one->storeTranslations();
+                if (!$this->content[$field] instanceof I18NString) {
+                    $this->content[$field] = $one;
+                    $this->content_db[$field] = clone $one;
+                }
+            }
+
+            // Apply callbacks
+            $this->applyCallbacks($this->isNew() ? 'after_create' : 'after_update');
+        }
+        $rel_ret = $this->storeRelations();
+
+        $this->applyCallbacks('after_store');
+
+        if ($ret || $rel_ret) {
+            $this->restore();
+        }
+        return $ret + $rel_ret;
+    }
+
+    /**
+     * sends a store message to all initialized related objects
+     * if a relation has a callback for 'on_store' configured, the callback
+     * is instead invoked
+     *
+     * @param null|array|string $only_these
+     * @return int|false number addition of all return values, false if none was called
+     */
+    protected function storeRelations($only_these = null)
+    {
+        $ret = false;
+        if (is_string($only_these)) {
+            $only_these = words($only_these);
+        }
+        $relations = array_keys($this->relations);
+        if (is_array($only_these)) {
+            $only_these = array_filter(array_map(function ($s) {
+                return is_string($s) ? strtolower($s) : null;
+            }, $only_these));
+            $relations = array_intersect($only_these, $relations);
+        }
+        foreach ($relations as $relation) {
+            $options = $this->getRelationOptions($relation);
+            if (isset($options['on_store']) &&
+            ($options['type'] === 'has_one' ||
+            $options['type'] === 'has_many' ||
+            $options['type'] === 'has_and_belongs_to_many')) {
+                if ($options['on_store'] instanceof Closure) {
+                    $ret += call_user_func($options['on_store'], $this, $relation);
+                } elseif (isset($this->relations[$relation])) {
+                    $foreign_key_value = call_user_func($options['assoc_func_params_func'], $this);
+                    if ($options['type'] === 'has_one') {
+                        call_user_func($options['assoc_foreign_key_setter'], $this->{$relation}, $foreign_key_value);
+                        $ret = call_user_func([$this->{$relation}, 'store']);
+                    } elseif ($options['type'] === 'has_many') {
+                        foreach ($this->{$relation} as $r) {
+                            call_user_func($options['assoc_foreign_key_setter'], $r, $foreign_key_value);
+                        }
+                        $ret += array_sum(call_user_func([$this->{$relation}, 'sendMessage'], 'store'));
+                        $ret += array_sum(call_user_func([$this->{$relation}->getDeleted(), 'sendMessage'], 'delete'));
+                    } else {
+                        call_user_func([$this->{$relation}, 'sendMessage'], 'store');
+                        $to_delete = array_filter($this->{$relation}->getDeleted()->pluck($options['assoc_foreign_key']));
+                        $to_insert = array_filter($this->{$relation}->pluck($options['assoc_foreign_key']));
+                        $sql = "DELETE FROM `" . $options['thru_table'] ."` WHERE `" . $options['thru_key'] ."` = ? AND `" . $options['thru_assoc_key'] . "` = ?";
+                        $st = DBManager::get()->prepare($sql);
+                        foreach ($to_delete as $one_value) {
+                            $st->execute([$foreign_key_value, $one_value]);
+                            $ret += $st->rowCount();
+                        }
+                        $sql = "INSERT IGNORE INTO `" . $options['thru_table'] ."` SET `" . $options['thru_key'] ."` = ?, `" . $options['thru_assoc_key'] . "` = ?";
+                        $st = DBManager::get()->prepare($sql);
+                        foreach ($to_insert as $one_value) {
+                            $st->execute([$foreign_key_value, $one_value]);
+                            $ret += $st->rowCount();
+                        }
+                    }
+                }
+            }
+        }
+        return $ret;
+    }
+
+    /**
+     * set chdate column to current timestamp
+     * @return boolean
+     */
+    function triggerChdate()
+    {
+        if ($this->db_fields()['chdate']) {
+            $this->content['chdate'] = time();
+            if ($where_query = $this->getWhereQuery()) {
+                DBManager::get()->exec("UPDATE `{$this->db_table()}` SET chdate={$this->content['chdate']}
+                            WHERE ". join(" AND ", $where_query));
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    /**
+     * delete entry from database
+     * the object is cleared, but is not(!) turned to new state
+     * @return bool|int number of deleted rows
+     */
+    function delete()
+    {
+        $ret = false;
+        if (!$this->isDeleted() && !$this->isNew()) {
+            if ($this->applyCallbacks('before_delete') === false) {
+                return false;
+            }
+            $ret = $this->deleteRelations();
+            $where_query = $this->getWhereQuery();
+            if ($where_query) {
+                $query = "DELETE FROM `{$this->db_table()}` WHERE "
+                        . join(" AND ", $where_query);
+                $ret += DBManager::get()->exec($query);
+            }
+            $this->is_deleted = true;
+            $this->applyCallbacks('after_delete');
+
+            // Remove i18n translations
+            if (I18N::isEnabled()) {
+                foreach (array_keys($this->i18n_fields()) as $field) {
+                    if ($this->content[$field] instanceof I18NString) {
+                        $this->content[$field]->removeTranslations();
+                    }
+                }
+            }
+        }
+        $this->setData([], true);
+        return $ret;
+    }
+
+    /**
+     * sends a delete message to all related objects
+     * if a relation has a callback for 'on_delete' configured, the callback
+     * is invoked instead
+     *
+     * @return bool|int addition of all return values, false if none was called
+     */
+    protected function deleteRelations()
+    {
+        $ret = false;
+        foreach (array_keys($this->relations) as $relation) {
+            $options = $this->getRelationOptions($relation);
+            if (isset($options['on_delete']) &&
+                ($options['type'] === 'has_one' ||
+                $options['type'] === 'has_many' ||
+                $options['type'] === 'has_and_belongs_to_many')) {
+                if ($options['on_delete'] instanceof Closure) {
+                    $ret += call_user_func($options['on_delete'], $this, $relation);
+                } else {
+                    if ($options['type'] === 'has_one' || $options['type'] === 'has_many') {
+                        $this->initRelation($relation);
+                        if (isset($this->relations[$relation])) {
+                            if ($options['type'] === 'has_one') {
+                                $ret += call_user_func([$this->{$relation}, 'delete']);
+                            } elseif ($options['type'] === 'has_many') {
+                                $ret += array_sum(call_user_func([$this->{$relation}, 'sendMessage'], 'delete'));
+                            }
+                        }
+                    } else {
+                        $foreign_key_value = call_user_func($options['assoc_func_params_func'], $this);
+                        $sql = "DELETE FROM `" . $options['thru_table'] ."` WHERE `" . $options['thru_key'] ."` = ?";
+                        $st = DBManager::get()->prepare($sql);
+                        $st->execute([$foreign_key_value]);
+                        $ret += $st->rowCount();
+                    }
+                }
+                $this->relations[$relation] = null;
+            }
+        }
+        return $ret;
+    }
+
+    /**
+     * init internal content arrays with nulls or defaults
+     *
+     * @throws UnexpectedValueException if there is an unmatched alias
+     * @return void
+     */
+    protected function initializeContent()
+    {
+        $this->content = [];
+        foreach (array_keys($this->db_fields()) as $field) {
+            $this->content[$field] = null;
+            $this->content_db[$field] = null;
+            $this->setValue($field, $this->getDefaultValue($field));
+        }
+        foreach ($this->alias_fields() as $alias => $field) {
+            if (isset($this->db_fields()[$field])) {
+                $this->content[$alias] =& $this->content[$field];
+                $this->content_db[$alias] =& $this->content_db[$field];
+            } else {
+                throw new UnexpectedValueException(sprintf('Column %s not found for alias %s', $field, $alias));
+            }
+        }
+        foreach (array_keys($this->relations) as $one) {
+            $this->relations[$one] = null;
+        }
+        $this->additional_data = [];
+    }
+
+    /**
+     * checks if at least one field was modified since last restore
+     *
+     * @return boolean
+     */
+    public function isDirty()
+    {
+        foreach (array_keys($this->db_fields()) as $field) {
+            if ($this->isFieldDirty($field)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * checks if given field was modified since last restore
+     *
+     * @param string $field
+     * @return boolean
+     */
+    public function isFieldDirty($field)
+    {
+        $field = strtolower($field);
+        if ($this->content[$field] === null || $this->content_db[$field] === null) {
+            return $this->content[$field] !== $this->content_db[$field];
+        } else if ($this->content[$field] instanceof I18NString || $this->content_db[$field] instanceof I18NString) {
+            return $this->content[$field] != $this->content_db[$field];
+        } else {
+            return (string)$this->content[$field] !== (string)$this->content_db[$field];
+        }
+    }
+
+    /**
+     * reverts value of given field to last restored value
+     *
+     * @param string $field
+     * @return mixed the restored value
+     */
+    public function revertValue($field)
+    {
+        $field = strtolower($field);
+        return ($this->content[$field] = $this->content_db[$field]);
+    }
+
+    /**
+     * returns unmodified value of given field
+     *
+     * @param string $field
+     * @throws InvalidArgumentException
+     * @return mixed
+     */
+    public function getPristineValue($field)
+    {
+        $field = strtolower($field);
+        if (array_key_exists($field, $this->content_db)) {
+            return $this->content_db[$field];
+        } else {
+            throw new InvalidArgumentException(get_class($this) . '::'. $field . ' not found.');
+        }
+    }
+
+    /**
+     * intitalize a relationship and get related record(s)
+     *
+     * @param string $relation name of relation
+     * @throws InvalidArgumentException if the relation does not exists
+     * @return void
+     */
+    public function initRelation($relation)
+    {
+        if (!array_key_exists($relation, $this->relations)) {
+            throw new InvalidArgumentException('Unknown relation: ' . $relation);
+        }
+        if ($this->relations[$relation] === null) {
+            $options = $this->getRelationOptions($relation);
+            $to_call = [$options['class_name'], $options['assoc_func']];
+            if (!is_callable($to_call)) {
+                throw new RuntimeException('assoc_func: ' . join('::', $to_call) . ' is not callable.' );
+            }
+            $params = $options['assoc_func_params_func'];
+            if ($options['type'] === 'has_many') {
+                $records = function($record) use ($to_call, $params, $options) {
+                    $p = (array)$params($record);
+                    return call_user_func_array($to_call, array_merge(count($p) ? $p : [null], [$options['order_by'] ?? null]));
+                };
+                $this->relations[$relation] = new SimpleORMapCollection($records, $options, $this);
+            } elseif ($options['type'] === 'has_and_belongs_to_many') {
+                $records = function($record) use ($to_call, $params, $options) {$p = (array)$params($record); return call_user_func_array($to_call, array_merge(count($p) ? $p : [null], [$options]));};
+                $this->relations[$relation] = new SimpleORMapCollection($records, $options, $this);
+            } else {
+                $p = (array)$params($this);
+                $records = call_user_func_array($to_call, count($p) ? $p : [null]);
+                $result = is_array($records) ? ($records[0] ?? null) : $records;
+                $this->relations[$relation] = $result;
+            }
+        }
+    }
+
+    /**
+     * clear data for a relationship
+     *
+     * @param string $relation name of relation
+     * @throws InvalidArgumentException if teh relation does not exists
+     * @return void
+     */
+    public function resetRelation($relation)
+    {
+        if (!array_key_exists($relation, $this->relations)) {
+            throw new InvalidArgumentException('Unknown relation: ' . $relation);
+        }
+        $this->relations[$relation] = null;
+    }
+
+    /**
+     * invoke registered callbacks for given type
+     * if one callback returns false the following will not
+     * be invoked
+     *
+     * @param string $type type of callback
+     * @return bool return value from last callback
+     */
+    protected function applyCallbacks($type)
+    {
+        $ok = true;
+        foreach ($this->registered_callbacks()[$type] as $cb) {
+            if ($cb instanceof Closure) {
+                $function =  $cb;
+                $params = [$this, $type, $cb];
+            } else {
+                $function = [$this, $cb];
+                $params = [$type];
+            };
+            $ok = call_user_func_array($function, $params);
+            if ($ok === false) {
+                break;
+            }
+        }
+        return $ok;
+    }
+
+    /**
+     * register given callback for one or many possible callback types
+     * callback param could be a closure or method name of current class
+     *
+     * @param string|array $types types to register callback for
+     * @param callable $cb callback
+     * @throws InvalidArgumentException if the callback type is not known
+     * @return number of registered callbacks
+     */
+    protected static function registerCallback($types, $cb)
+    {
+        trigger_error(__METHOD__ . ' is deprecated. Please use the configuration in configure().', E_USER_DEPRECATED);
+
+        $types = is_array($types) ? $types : words($types);
+        $reg = 0;
+        foreach ($types as $type) {
+            if (isset(static::registered_callbacks()[$type])) {
+                $found = array_search($cb, self::$config[static::class]['registered_callbacks'][$type], true);
+                if ($found === false) {
+                    self::$config[static::class]['registered_callbacks'][$type][] = $cb;
+                    $reg++;
+                }
+            } else {
+                throw new InvalidArgumentException('Unknown callback type: ' . $type);
+            }
+        }
+        return $reg;
+    }
+
+    /**
+     * unregister given callback for one or many possible callback types
+     *
+     * @param string|array $types types to unregister callback for
+     * @param mixed $cb
+     * @throws InvalidArgumentException if the callback type is not known
+     * @return number of unregistered callbacks
+     */
+    protected static function unregisterCallback($types, $cb)
+    {
+        trigger_error(__METHOD__ . ' is deprecated. Please use the configuration in configure().', E_USER_DEPRECATED);
+
+        $types = is_array($types) ? $types : words($types);
+        foreach ($types as $type) {
+            if (isset(static::registered_callbacks()[$type])) {
+                $found = array_search($cb, self::$config[static::class]['registered_callbacks'][$type], true);
+                if ($found !== false) {
+                    $unreg++;
+                    unset(self::$config[static::class]['registered_callbacks'][$type][$found]);
+                }
+            } else {
+                throw new InvalidArgumentException('Unknown callback type: ' . $type);
+            }
+        }
+        return $unreg;
+    }
+
+    /**
+     * default callback used to map specific callbacks to NotificationCenter
+     *
+     * @param string $cb_type callback type
+     * @return void|boolean
+     */
+    protected function cbNotificationMapper($cb_type)
+    {
+        if (isset($this->notification_map()[$cb_type])) {
+            try {
+                foreach(words($this->notification_map()[$cb_type]) as $notification) {
+                    NotificationCenter::postNotification($notification, $this);
+                }
+            } catch (NotificationVetoException $e) {
+                return false;
+            }
+        }
+    }
+
+    /**
+     * default callback used to map specific callbacks to NotificationCenter
+     *
+     * @param string $cb_type callback type
+     * @return void|boolean
+     */
+    protected function cbAfterInitialize($cb_type)
+    {
+        foreach (array_keys($this->db_fields()) as $field) {
+            if (is_object($this->content[$field])) {
+                $this->content_db[$field] = clone $this->content[$field];
+            } else {
+                $this->content_db[$field] = $this->content[$field];
+            }
+        }
+    }
+
+    /**
+     * default setter used to proxy serialized fields with
+     * ArrayObjects
+     *
+     * @param string $field column name
+     * @param mixed $value value
+     * @return mixed
+     */
+     protected function setSerializedValue($field, $value)
+     {
+         $object_type = $this->serialized_fields()[$field];
+         if (is_null($value) || $value instanceof $object_type) {
+             $this->content[$field] = $value;
+         } else {
+             $this->content[$field] = new $object_type($value);
+         }
+         return $this->content[$field];
+     }
+
+    /**
+     * default setter used to proxy I18N fields with
+     * I18NString
+     *
+     * @param string $field column name
+     * @param mixed $value value
+     * @return mixed
+     */
+    protected function setI18nValue($field, $value)
+    {
+        $meta = ['object_id' => $this->getId(),
+                 'table'     => $this->db_table(),
+                 'field'     => $field];
+        if ($value instanceof I18NString) {
+            $value->setMetadata($meta);
+            $this->content[$field] = $value;
+        } else {
+            $this->content[$field] = new I18NString($value, null, $meta);
+        }
+        return $this->content[$field];
+    }
+
+     /**
+      * Cleans up this object. This essentially reset all relations of
+      * this object and marks them as unused so that the garbage collector may
+      * remove the objects.
+      *
+      * Use this function when you ran into memory problems and need to free
+      * some memory;
+      *
+      * @return void
+      */
+     public function cleanup()
+     {
+         foreach ($this->relations as $relation => $object) {
+             if ($object instanceof SimpleORMap || $object instanceof SimpleORMapCollection) {
+                 $this->relations[$relation]->cleanup();
+             }
+             $this->resetRelation($relation);
+         }
+     }
+}
diff --git a/lib/classes/SimpleORMapCollection.php b/lib/classes/SimpleORMapCollection.php
new file mode 100644
index 0000000..20162e5
--- /dev/null
+++ b/lib/classes/SimpleORMapCollection.php
@@ -0,0 +1,258 @@
+<?php
+/**
+ * SimpleORMapCollection.php
+ * simple object-relational mapping
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      André Noack <noack@data-quest.de>
+ * @copyright   2012 Stud.IP Core-Group
+ * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
+ * @category    Stud.IP
+ *
+ * @extends SimpleCollection<SimpleORMap>
+ *
+ * @template T of SimpleORMap
+ */
+class SimpleORMapCollection extends SimpleCollection
+{
+    /**
+     * @var int Exception error code denoting a wrong type of objects.
+     */
+    const WRONG_OBJECT_TYPE = 1;
+
+    /**
+     * @var int Exception error code denoting that an object of this `id` already exists.
+     */
+    const OBJECT_EXISTS = 2;
+
+    /**
+     * the record object this collection belongs to
+     *
+     * @var ?SimpleORMap
+     */
+    protected $related_record;
+
+    /**
+     * relation options
+     * @var array
+     */
+    protected $relation_options = [];
+
+    /**
+     * creates a collection from an array of objects
+     * all objects should be of the same type
+     *
+     * @throws InvalidArgumentException if first entry is not SimpleOrMap
+     * @param T[] $data array with SimpleORMap objects
+     * @param bool $strict check every element for correct type and unique pk
+     * @return SimpleORMapCollection<T>
+     */
+    public static function createFromArray(array $data, $strict = true)
+    {
+        $ret = new SimpleORMapCollection();
+        if (count($data)) {
+            $first = current($data);
+            if ($first instanceof SimpleORMap) {
+                $ret->setClassName(get_class($first));
+                if ($strict) {
+                    foreach ($data as $one) {
+                        $ret[] = $one;
+                    }
+                } else {
+                    $ret->exchangeArray($data);
+                }
+            } else {
+                throw new InvalidArgumentException('This collection only accepts objects derived from SimpleORMap', self::WRONG_OBJECT_TYPE);
+            }
+        }
+        return $ret;
+    }
+
+    /**
+     * Constructor
+     *
+     * @param ?Closure         $finder  callable to fill collection
+     * @param ?array           $options relationship options
+     * @param SimpleORMap|null $record  related record
+     */
+    public function __construct(Closure $finder = null, array $options = null, SimpleORMap $record = null)
+    {
+        $this->relation_options = $options;
+        $this->related_record = $record;
+        parent::__construct($finder === null ? [] : $finder);
+    }
+
+    /**
+     * Sets the value at the specified index
+     * checks if the value is an object of specified class
+     *
+     * @see ArrayObject::offsetSet()
+     * @throws InvalidArgumentException if the given model does not fit (wrong type or id)
+     */
+    public function offsetSet($index, $newval): void
+    {
+        if (!is_null($index)) {
+            $index = (int)$index;
+        }
+        if (!is_a($newval, $this->getClassName())) {
+            throw new InvalidArgumentException('This collection only accepts objects of type: ' .  $this->getClassName(), self::WRONG_OBJECT_TYPE);
+        }
+        if ($this->related_record && $this->relation_options['type'] === 'has_many') {
+            $foreign_key_value = call_user_func($this->relation_options['assoc_func_params_func'], $this->related_record);
+            call_user_func($this->relation_options['assoc_foreign_key_setter'], $newval, $foreign_key_value);
+        }
+        if ($newval->id !== null) {
+            $exists = $this->find($newval->id);
+            if ($exists) {
+                throw new InvalidArgumentException('Element could not be appended, element with id: ' . $exists->id . ' is in the way', self::OBJECT_EXISTS);
+            }
+        }
+        parent::offsetSet($index, $newval);
+    }
+
+    /**
+     * sets the allowed class name
+     * @param class-string $class_name
+     * @return void
+     */
+    public function setClassName($class_name)
+    {
+        $this->relation_options['class_name'] = strtolower($class_name);
+        $this->deleted->relation_options['class_name'] = strtolower($class_name);
+    }
+
+    /**
+     * sets the related record
+     *
+     * @param SimpleORMap $record
+     * @return void
+     */
+    public function setRelatedRecord(SimpleORMap $record)
+    {
+        $this->related_record = $record;
+    }
+
+    /**
+     * gets the allowed classname
+     *
+     * @return string
+     */
+    public function getClassName()
+    {
+        return strtolower($this->relation_options['class_name']);
+    }
+
+    /**
+     * reloads the elements of the collection
+     * by calling the finder function
+     *
+     * @throws InvalidArgumentException
+     * @return ?int number of records after refresh
+     */
+    public function refresh()
+    {
+        if (is_callable($this->finder)) {
+            $data = call_user_func($this->finder, $this->related_record);
+            foreach ($data as $one) {
+                if (!is_a($one, $this->getClassName())) {
+                    throw new InvalidArgumentException('This collection only accepts objects of type: ' .  $this->getClassName(), self::WRONG_OBJECT_TYPE);
+                }
+            }
+            $this->exchangeArray($data);
+            $this->deleted->exchangeArray([]);
+            return $this->last_count = $this->count();
+        }
+
+        return null;
+    }
+
+    /**
+     * returns element with given primary key value
+     *
+     * @param string $value primary key value to search for
+     * @return ?T
+     */
+    public function find($value)
+    {
+        return $this->findOneBy('id', $value);
+    }
+
+    /**
+     * returns the collection as grouped array
+     * first param is the column to group by, it becomes the key in
+     * the resulting array, default is pk. Limit returned fields with second param
+     * The grouped entries can optoionally go through the given
+     * callback. If no callback is provided, only the first grouped
+     * entry is returned, suitable for grouping by unique column
+     *
+     * @param string $group_by the column to group by, pk if ommitted
+     * @param mixed $only_these_fields limit returned fields
+     * @param ?callable $group_func closure to aggregate grouped entries
+     * @return array assoc array
+     */
+    public function toGroupedArray($group_by = 'id', $only_these_fields = null, callable $group_func = null)
+    {
+        $result = [];
+        foreach ($this as $record) {
+            $key = $record->getValue($group_by);
+            if (is_array($key)) {
+                $key = join('_', $key);
+            }
+            $result[$key][] = $record->toArray($only_these_fields);
+        }
+        if ($group_func === null) {
+            $group_func = 'current';
+        }
+        return array_map($group_func, $result);
+    }
+
+    /**
+     * mark element(s) for deletion
+     * element(s) with given primary key are moved to
+     * internal deleted collection
+     *
+     * @param string $id primary key of element
+     * @return int number of unsetted elements
+     */
+    public function unsetByPk($id)
+    {
+        return $this->unsetBy('id', $id);
+    }
+
+    /**
+     * merge in another collection, elements must be of
+     * the same type, if an element already exists it is
+     * replaced or ignored depending on second param
+     *
+     * @param SimpleORMapCollection $a_collection
+     * @param string $mode 'replace' or 'ignore'
+     * @return void
+     */
+    public function merge(SimpleCollection $a_collection, string $mode = 'ignore')
+    {
+        $mode = func_get_arg(1);
+        foreach ($a_collection as $element) {
+            try {
+                /**
+                 * @throws InvalidArgumentException
+                 * @see SimpleORMapCollection::offsetSet()
+                 */
+                $this[] = $element;
+            } catch (InvalidArgumentException $e) {
+                if ($e->getCode() === self::OBJECT_EXISTS) {
+                    if ($mode === 'replace') {
+                        $this->unsetByPk($element->id);
+                        $this[] = $element;
+                    } // else $mode means 'ignore'
+                } else {
+                    throw $e;
+                }
+            }
+        }
+        $this->storage = array_values($this->storage);
+    }
+}
diff --git a/lib/classes/Siteinfo.php b/lib/classes/Siteinfo.php
index 4722b93..4a969ee 100644
--- a/lib/classes/Siteinfo.php
+++ b/lib/classes/Siteinfo.php
@@ -281,7 +281,7 @@ class SiteinfoMarkupEngine {
 
     function __construct() {
         $this->db = DBManager::get();
-        $this->template_factory = new Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'].'/app/views/siteinfo/markup/');
+        $this->template_factory = new Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'].'/app/views/siteinfo/markup/');
         $this->siteinfoMarkup("/\(:version:\)/", [$this, 'version']);
         $this->siteinfoMarkup("/\(:uniname:\)/", [$this, 'uniName']);
         $this->siteinfoMarkup("/\(:unicontact:\)/", [$this, 'uniContact']);
@@ -419,7 +419,7 @@ class SiteinfoMarkupEngine {
     }
 
     function coregroup() {
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         if (!($remotefile = $cache->read('coregroup'))) {
             $remotefile = file_get_contents('https://develop.studip.de/studip/extern.php?module=Persons&config_id=8d1dafc3afca2bce6125d57d4119b631&range_id=4498a5bc62d7974d0a0ac3e97aca5296', false, get_default_http_stream_context('https://develop.studip.de'));
             $cache->write('coregroup', $remotefile);
@@ -428,7 +428,7 @@ class SiteinfoMarkupEngine {
     }
 
     function toplist($item) {
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         if ($found_in_cache = $cache->read(__METHOD__ . $item)) {
             return $found_in_cache;
         }
@@ -480,7 +480,7 @@ class SiteinfoMarkupEngine {
                 // get TopTen of seminars from all ForumModules and add up the
                 // count for seminars with more than one active ForumModule
                 // to get a combined toplist
-                foreach (PluginEngine::getPlugins('ForumModule') as $plugin) {
+                foreach (PluginEngine::getPlugins(ForumModule::class) as $plugin) {
                     $new_seminars = $plugin->getTopTenSeminars();
                     foreach ($new_seminars as $sem) {
                         if (!isset($seminars[$sem['seminar_id']])) {
@@ -531,7 +531,7 @@ class SiteinfoMarkupEngine {
     }
 
     function indicator($key) {
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         if ($found_in_cache = $cache->read(__METHOD__ . $key)) {
             return $found_in_cache;
         }
@@ -576,11 +576,7 @@ class SiteinfoMarkupEngine {
                                    "title" => _("Fragebögen"),
                                    "detail" => "",
                                    "constraint" => Config::get()->VOTE_ENABLE];
-        $indicator['evaluation'] = ["count" => ['count_table_rows','eval'],
-                                         "title" => _("Evaluationen"),
-                                         "detail" => "",
-                                         "constraint" => Config::get()->VOTE_ENABLE];
-        $indicator['wiki_pages'] = ["query" => "SELECT COUNT(DISTINCT keyword) AS count FROM wiki",
+        $indicator['wiki_pages'] = ["query" => "SELECT COUNT(*) AS count FROM wiki_pages",
                                          "title" => _("Wiki-Seiten"),
                                          "detail" => "",
                                          "constraint" => Config::get()->WIKI_ENABLE];
@@ -593,7 +589,7 @@ class SiteinfoMarkupEngine {
             $count = 0;
 
             // sum up number of postings for all availabe ForumModules
-            foreach (PluginEngine::getPlugins('ForumModule') as $plugin) {
+            foreach (PluginEngine::getPlugins(ForumModule::class) as $plugin) {
                 $count += $plugin->getNumberOfPostings();
             }
 
@@ -663,7 +659,7 @@ function language_filter($input) {
 }
 
 function stripforeignlanguage($language, $text) {
-    list($primary, $sub) = explode('_',$_SESSION['_language']);
+    [$primary, $sub] = explode('_',$_SESSION['_language']);
     if ($language === $primary || $language === $_SESSION['_language']) {
         return str_replace('\"', '"', $text);
     } else {
diff --git a/lib/classes/StudipArrayObject.class.php b/lib/classes/StudipArrayObject.php
index fe9aad1..da7e66e 100644
--- a/lib/classes/StudipArrayObject.class.php
+++ b/lib/classes/StudipArrayObject.php
@@ -135,6 +135,38 @@ class StudipArrayObject implements IteratorAggregate, ArrayAccess, Serializable,
     }
 
     /**
+     * Called when serializing an ArrayObject
+     */
+    public function __serialize(): array
+    {
+        return get_object_vars($this);
+    }
+
+    /**
+     * Called when unserializing an ArrayObject
+     */
+    public function __unserialize(array $data): void
+    {
+        foreach ($data as $k => $v) {
+            switch ($k) {
+                case 'flag':
+                    $this->setFlags($v);
+                    break;
+                case 'storage':
+                    $this->exchangeArray($v);
+                    break;
+                case 'iteratorClass':
+                    $this->setIteratorClass($v);
+                    break;
+                case 'protectedProperties':
+                    break;
+                default:
+                    $this->__set($k, $v);
+            }
+        }
+    }
+
+    /**
      * Appends the value
      *
      * @param  mixed $value
@@ -157,13 +189,8 @@ class StudipArrayObject implements IteratorAggregate, ArrayAccess, Serializable,
 
     /**
      * Get the number of public properties in the ArrayObject
-     *
-     * @return int
-     *
-     * @todo Add int return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function count()
+    public function count(): int
     {
         return count($this->storage);
     }
@@ -216,13 +243,8 @@ class StudipArrayObject implements IteratorAggregate, ArrayAccess, Serializable,
 
     /**
      * Create a new iterator from an ArrayObject instance
-     *
-     * @return \Iterator
-     *
-     * @todo Add Traversable return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         $class = $this->iteratorClass;
 
@@ -273,12 +295,8 @@ class StudipArrayObject implements IteratorAggregate, ArrayAccess, Serializable,
      * Returns whether the requested key exists
      *
      * @param  mixed $key
-     * @return bool
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetExists($key)
+    public function offsetExists($key): bool
     {
         return isset($this->storage[$key]);
     }
@@ -287,12 +305,8 @@ class StudipArrayObject implements IteratorAggregate, ArrayAccess, Serializable,
      * Returns the value at the specified key
      *
      * @param  mixed $key
-     * @return mixed
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($key)
+    public function offsetGet($key): mixed
     {
         $ret = null;
         if (!$this->offsetExists($key)) {
@@ -308,12 +322,8 @@ class StudipArrayObject implements IteratorAggregate, ArrayAccess, Serializable,
      *
      * @param  mixed $key
      * @param  mixed $value
-     * @return void
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetSet($key, $value)
+    public function offsetSet($key, $value): void
     {
         if (is_null($key)) {
             $this->append($value);
@@ -326,12 +336,8 @@ class StudipArrayObject implements IteratorAggregate, ArrayAccess, Serializable,
      * Unsets the value at the specified key
      *
      * @param  mixed $key
-     * @return void
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($key)
+    public function offsetUnset($key): void
     {
         if ($this->offsetExists($key)) {
             unset($this->storage[$key]);
diff --git a/lib/classes/StudipAutoloader.php b/lib/classes/StudipAutoloader.php
index 7054478..883adc7 100644
--- a/lib/classes/StudipAutoloader.php
+++ b/lib/classes/StudipAutoloader.php
@@ -52,8 +52,8 @@ class StudipAutoloader
     // file is found quickly and unneccessary, costly calls to file_exists()
     // can be avoided.
     protected static $file_extensions = [
-        '.class.php',
         '.php',
+        '.class.php',
         '.interface.php',
     ];
 
diff --git a/lib/classes/StudipCache.class.php b/lib/classes/StudipCache.class.php
deleted file mode 100644
index ba929f9..0000000
--- a/lib/classes/StudipCache.class.php
+++ /dev/null
@@ -1,94 +0,0 @@
-<?php
-/**
- * An interface which has to be implemented by instances returned from
- * StudipCacheFactory#getCache
- *
- * @package    studip
- * @subpackage lib
- *
- * @author     Marco Diedrich (mdiedric@uos)
- * @author     Marcus Lunzenauer (mlunzena@uos.de)
- * @copyright  (c) Authors
- * @since      1.6
- * @license    GPL2 or any later version
- */
-
-interface StudipCache
-{
-    const DEFAULT_EXPIRATION = 12 * 60 * 60; // 12 hours
-
-    /**
-     * Expire item from the cache.
-     *
-     * Example:
-     *
-     *   # expires foo
-     *   $cache->expire('foo');
-     *
-     * @param string $arg a single key
-     */
-    public function expire($arg);
-
-    /**1
-     * Expire all items from the cache.
-     */
-    public function flush();
-
-    /**
-     * Retrieve item from the server.
-     *
-     * Example:
-     *
-     *   # reads foo
-     *   $foo = $cache->reads('foo');
-     *
-     * @param string $arg a single key
-     *
-     * @return mixed    the previously stored data if an item with such a key
-     *                  exists on the server or FALSE on failure.
-     */
-    public function read($arg);
-
-    /**
-     * Store data at the server.
-     *
-     * @param string $name     the item's key.
-     * @param mixed  $content  the item's content (will be serialized if necessary).
-     * @param int    $expires  the item's expiry time in seconds. Optional, defaults to 12h.
-     *
-     * @return bool     returns TRUE on success or FALSE on failure.
-     */
-    public function write($name, $content, $expires = self::DEFAULT_EXPIRATION);
-
-    /**
-     * @return string A translateable display name for this cache class.
-     */
-    public static function getDisplayName(): string;
-
-    /**
-     * Get some statistics from cache, like number of entries, hit rate or
-     * whatever the underlying cache provides.
-     * Results are returned in form of an array like
-     *      "[
-     *          [
-     *              'name' => <displayable name>
-     *              'value' => <value of the current stat>
-     *          ]
-     *      ]"
-     *
-     * @return array
-     */
-    public function getStats(): array;
-
-    /**
-     * Return the Vue component name and props that handle configuration.
-     * The associative array is of the form
-     *  [
-     *      'component' => <Vue component name>,
-     *      'props' => <Properties for component>
-     *  ]
-     *
-     * @return array
-     */
-    public static function getConfig(): array;
-}
diff --git a/lib/classes/StudipCachedArray.php b/lib/classes/StudipCachedArray.php
index 18bb55b..46723f4 100644
--- a/lib/classes/StudipCachedArray.php
+++ b/lib/classes/StudipCachedArray.php
@@ -27,10 +27,10 @@ class StudipCachedArray implements ArrayAccess
      * @param int    $duration Duration in seconds for which the item shall be
      *                         stored
      */
-    public function __construct(string $key, int $duration = StudipCache::DEFAULT_EXPIRATION)
+    public function __construct(string $key, int $duration = \Studip\Cache\Cache::DEFAULT_EXPIRATION)
     {
         $this->key = self::class . "/{$key}";
-        $this->cache = StudipCacheFactory::getCache();
+        $this->cache = \Studip\Cache\Factory::getCache();
         $this->duration = $duration;
         $this->hash = $this->getHash();
 
@@ -71,13 +71,8 @@ class StudipCachedArray implements ArrayAccess
      * Returns the value at given offset or null if it doesn't exist.
      *
      * @param string $offset Offset
-     *
-     * @return mixed
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         $this->loadData($offset);
         return $this->data[$offset];
@@ -121,11 +116,14 @@ class StudipCachedArray implements ArrayAccess
     protected function loadData(string $offset)
     {
         if (!array_key_exists($offset, $this->data)) {
-            $cached = $this->cache->read($this->getCacheKey($offset));
-            $this->data[$offset] = $this->swapNullAndFalse($cached);
+            // Get the cache item from the cache:
+            $item = $this->cache->getItem($this->getCacheKey($offset));
+            if ($item->isHit()) {
+                $this->data[$offset] = $this->swapNullAndFalse($item->get());
+            }
         }
 
-        return $this->data[$offset];
+        return $this->data[$offset] ?? null;
     }
 
     /**
@@ -137,13 +135,12 @@ class StudipCachedArray implements ArrayAccess
      */
     protected function storeData(string $offset): void
     {
-        $data = $this->swapNullAndFalse($this->data[$offset]);
-
-        $this->cache->write(
+        $item = new \Studip\Cache\Item(
             $this->getCacheKey($offset),
-            $data,
+            $this->swapNullAndFalse($this->data[$offset]),
             $this->duration
         );
+        $this->cache->save($item);
     }
 
     /**
diff --git a/lib/classes/StudipController.php b/lib/classes/StudipController.php
new file mode 100644
index 0000000..a908a47
--- /dev/null
+++ b/lib/classes/StudipController.php
@@ -0,0 +1,885 @@
+<?php
+/*
+ * StudipController.php - studip controller base class
+ * Copyright (c) 2009  Elmar Ludwig
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+use DebugBar\DebugBar;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Writer\Csv;
+use PhpOffice\PhpSpreadsheet\Writer\Xlsx;
+
+/**
+ * @property StudipResponse $response
+ */
+abstract class StudipController extends Trails\Controller
+{
+    use StudipControllerPropertiesTrait;
+
+    protected $with_session = false; //do we need to have a session for this controller
+    protected $allow_nobody = true; //should 'nobody' allowed for this controller or redirected to login?
+    protected $_autobind = false;
+
+    /**
+     * @return false|void
+     */
+    public function before_filter(&$action, &$args)
+    {
+        $this->current_action = $action;
+        // allow only "word" characters in arguments
+        $this->validate_args($args);
+
+        parent::before_filter($action, $args);
+
+        if ($this->with_session) {
+            # open session
+            page_open([
+                'sess' => 'Seminar_Session',
+                'auth' => $this->allow_nobody ? 'Seminar_Default_Auth' : 'Seminar_Auth',
+                'perm' => 'Seminar_Perm',
+                'user' => 'Seminar_User'
+            ]);
+
+            // show login-screen, if authentication is "nobody"
+            $GLOBALS['auth']->login_if((Request::get('again') || !$this->allow_nobody) && $GLOBALS['user']->id == 'nobody');
+
+            // Setup flash instance
+            $this->flash = Trails\Flash::instance();
+
+            // set up user session
+            include 'lib/seminar_open.php';
+        }
+
+        // Set generic attribute that indicates whether the request was sent
+        // via ajax or not
+        $this->via_ajax = Request::isXhr();
+
+        # Set base layout
+        #
+        # If your controller needs another layout, overwrite your controller's
+        # before filter:
+        #
+        #   class YourController extends AuthenticatedController {
+        #     function before_filter(&$action, &$args) {
+        #       parent::before_filter($action, $args);
+        #       $this->set_layout("your_layout");
+        #     }
+        #   }
+        #
+        # or unset layout by sending:
+        #
+        #   $this->set_layout(NULL)
+        #
+        $layout_file = Request::isXhr()
+                     ? 'layouts/dialog.php'
+                     : 'layouts/base.php';
+        $layout = $GLOBALS['template_factory']->open($layout_file);
+        $this->set_layout($layout);
+
+        $this->set_content_type('text/html;charset=utf-8');
+    }
+
+    /**
+     * Extended method to inject extended response object.
+     */
+    public function erase_response()
+    {
+        parent::erase_response();
+
+        $this->response = new StudipResponse();
+    }
+
+    /**
+     * Hooked perform method in order to inject body element id creation.
+     *
+     * In order to avoid clashes, these body element id will be joined
+     * with a minus sign. Otherwise the controller "x" with action
+     * "y_z" would be given the same id as the controller "x/y" with
+     * the action "z", namely "x_y_z". With the minus sign this will
+     * result in the ids "x-y_z" and "x_y-z".
+     *
+     * Plugins will always have a leading 'plugin-' and the decamelized
+     * plugin name in front of the id.
+     *
+     * @param String $unconsumed_path Path segment containing action and
+     *                                optionally arguments or format
+     * @return Trails\Response from parent controller
+     */
+    public function perform($unconsumed_path)
+    {
+        // Set body element id if it has not already been set
+        if (!PageLayout::hasBodyElementId()) {
+            $body_id = $this->getBodyElementIdForControllerAndAction($unconsumed_path);
+            PageLayout::setBodyElementId($body_id);
+        }
+
+        return parent::perform($unconsumed_path);
+    }
+
+    /**
+     * Callback function being called after an action is executed.
+     *
+     * @param string Name of the action to perform.
+     * @param array  An array of arguments to the action.
+     *
+     * @return void
+     */
+    public function after_filter($action, $args)
+    {
+        parent::after_filter($action, $args);
+
+        if (Request::isXhr() && !isset($this->response->headers['X-Title']) && PageLayout::hasTitle()) {
+            $this->response->add_header('X-Title', rawurlencode(PageLayout::getTitle()));
+        }
+        if (Request::isXhr() && !isset($this->response->headers['X-WikiLink']) && PageLayout::getHelpKeyword()) {
+            $this->response->add_header('X-WikiLink', format_help_url(PageLayout::getHelpKeyword()));
+        }
+
+        if ($this->with_session) {
+            page_close();
+        }
+    }
+
+    /**
+     * Validate arguments based on a list of given types. The types are:
+     * 'int', 'float', 'option' and 'string'. If the list of types is NULL
+     * or shorter than the argument list, 'option' is assumed for all
+     * remaining arguments. 'option' differs from Request::option() in
+     * that it also accepts the charaters '-' and ',' in addition to all
+     * word characters.
+     *
+     * Since Stud.IP 4.0 it is also possible to directly inject
+     * SimpleORMap objects. If types is NULL, the signature of the called
+     * action is analyzed and any type hint that matches a sorm class
+     * will be used to create an object using the argument as the id
+     * that is passed to the object's constructor.
+     *
+     * If $_autobind is set to true, the created object is also assigned
+     * to the controller so that it is available in a view.
+     *
+     * @param array $args  an array of arguments to the action
+     * @param array $types list of argument types (optional)
+     */
+    public function validate_args(&$args, $types = null)
+    {
+        $class_infos = [];
+
+        if ($types === null) {
+            $types = [];
+        }
+
+        if ($this->has_action($this->current_action)) {
+            $reflection = new ReflectionMethod($this, $this->current_action . '_action');
+            $parameters = $reflection->getParameters();
+            foreach ($parameters as $i => $parameter) {
+                $class_type = $parameter->getType();
+
+                if (
+                    !$class_type
+                    || !class_exists($class_type->getName())
+                    || !is_a($class_type->getName(), SimpleORMap::class, true)
+                ) {
+                    continue;
+                }
+
+                $types[$i] = 'sorm';
+                $class_infos[$i] = [
+                    'model'    => $class_type->getName(),
+                    'var'      => $parameter->getName(),
+                    'optional' => $parameter->isOptional(),
+                ];
+
+                if ($parameter->isOptional() && !isset($args[$i])) {
+                    $args[$i] = $parameter->getDefaultValue();
+                }
+            }
+        }
+
+        foreach ($args as $i => &$arg) {
+            $type = $types[$i] ?? 'option';
+            switch ($type) {
+                case 'int':
+                    $arg = (int) $arg;
+                    break;
+
+                case 'float':
+                    $arg = (float) strtr($arg, ',', '.');
+                    break;
+
+                case 'option':
+                    if (preg_match('/[^\\w,-]/', $arg)) {
+                        throw new Trails\Exception(400);
+                    }
+                    break;
+
+                case 'sorm':
+                    $info = $class_infos[$i];
+
+                    $id = null;
+                    if ($arg != -1) {
+                        $id = $arg;
+                    }
+                    if (mb_strpos($id, SimpleORMap::ID_SEPARATOR) !== false) {
+                        $id = explode(SimpleORMap::ID_SEPARATOR, $id);
+                    }
+
+                    $reflection = new ReflectionClass($info['model']);
+
+                    $sorm = $reflection->newInstance($id);
+                    if (!$info['optional'] && $sorm->isNew()) {
+                        throw new Trails\Exception(
+                            404,
+                            "Parameter {$info['var']} could not be resolved with value {$arg}"
+                        );
+                    }
+
+                    $arg = $sorm;
+                    if ($this->_autobind) {
+                        $this->{$info['var']} = $arg;
+                    }
+                    break;
+
+                case 'string':
+                    break;
+
+                default:
+                    throw new Trails\Exception(500, 'Unknown type "' . $type . '"');
+            }
+        }
+
+        reset($args);
+    }
+
+    /**
+     * Returns a URL to a specified route to your Trails application.
+     * without first parameter the current action is used
+     * if route begins with a / then the current controller ist prepended
+     * if second parameter is an array it is passed to URLHeper
+     *
+     * @param  string   a string containing a controller and optionally an action
+     * @param  string[] optional arguments
+     *
+     * @return string  a URL to this route
+     */
+    public function url_for($to = ''/* , ... */)
+    {
+        $args = func_get_args();
+
+        // Try to create route if none given
+        if ($to === '') {
+            $args[0] = isset($this->parent_controller)
+                     ? $this->parent_controller->current_action
+                     : $this->current_action;
+            return $this->action_url(...$args);
+        }
+
+        // Create url for a specific action
+        // TODO: This seems odd. You kinda specify an absolute path
+        //       to receive a relative url. Meh...
+        //
+        // @deprecated Do not use this, please!
+        if ($to[0] === '/') {
+            $args[0] = substr($to, 1);
+            return $this->action_url(...$args);
+        }
+
+        // Check for absolute URL
+        if ($this->isURL($to)) {
+            throw new InvalidArgumentException(__METHOD__ . ' cannot be used with absolute URLs');
+        }
+
+        // Extract fragment (if any)
+        if (strpos($to, '#') !== false) {
+            [$args[0], $fragment] = explode('#', $to);
+        }
+
+        // Extract parameters (if any)
+        $params = [];
+        if (is_array(end($args))) {
+            $params = array_pop($args);
+        }
+
+        // Map any sorm objects to their ids
+        $args = array_map(function ($arg) {
+            if (is_object($arg) && $arg instanceof SimpleORMap) {
+                return $arg->isNew() ? -1 : $arg->id;
+            }
+            return $arg;
+        }, $args);
+
+        $url = parent::url_for(...$args);
+
+        if (isset($fragment)) {
+            $url .= '#' . $fragment;
+        }
+        return URLHelper::getURL($url, $params);
+    }
+
+    /**
+     * Returns an escaped URL to a specified route to your Trails application.
+     * without first parameter the current action is used
+     * if route begins with a / then the current controller ist prepended
+     * if second parameter is an array it is passed to URLHeper
+     *
+     * @param  string   a string containing a controller and optionally an action
+     * @param  strings  optional arguments
+     *
+     * @return string  a URL to this route
+     */
+    public function link_for($to = ''/* , ... */)
+    {
+        return htmlReady($this->url_for(...func_get_args()));
+    }
+
+    /**
+     * Redirects the user another page. Accepts multiple parameters just like
+     * url_for().
+     *
+     * @param string $to
+     * @see StudipController::url_for()
+     */
+    public function redirect($to)
+    {
+        $to = $this->adjustToArguments(...func_get_args());
+
+        parent::redirect($to);
+    }
+
+    /**
+     * Relocate the user to another location. This is a specialized version
+     * of redirect that differs in two points:
+     *
+     * - relocate() will force the browser to leave the current dialog while
+     *   redirect would refresh the dialog's contents
+     * - relocate() accepts all the parameters that url_for() accepts so it's
+     *   no longer neccessary to chain url_for() and redirect()
+     *
+     * @param String $to Location to redirect to
+     */
+    public function relocate($to)
+    {
+        $to = $this->adjustToArguments(...func_get_args());
+
+        if (Request::isDialog()) {
+            $this->response->add_header('X-Location', encodeURI($to));
+            $this->render_nothing();
+        } else {
+            parent::redirect($to);
+        }
+    }
+
+    /**
+     * Returns a URL to a specified route to your Trails application, unless
+     * the parameter is already a valid URL (which is returned unchanged).
+     *
+     * If no absolute url or more than one argument is given, url_for() is
+     * used.
+     */
+    private function adjustToArguments(...$args): string
+    {
+        if (count($args) > 1 && $this->isURL($args[0])) {
+            throw new InvalidArgumentException('Method may not be used with a URL and multiple parameters');
+        }
+
+        if (count($args) === 1 && $this->isURL($args[0])) {
+            return $args[0];
+        }
+
+        return $this->url_for(...$args);
+    }
+
+    /**
+     * Returns whether the given parameter is a valid url.
+     *
+     * @param string $to
+     * @return bool
+     */
+    private function isURL(string $to): bool
+    {
+        return preg_match('#^(/|\w+://)#', $to);
+    }
+
+    /**
+     * Exception handler called when the performance of an action raises an
+     * exception.
+     *
+     * @param  object     the thrown exception
+     */
+    public function rescue($exception)
+    {
+        throw $exception;
+    }
+
+    /**
+     * render given data as json, data is converted to utf-8
+     *
+     * @param mixed $data
+     */
+    public function render_json($data)
+    {
+        $json = json_encode($data);
+
+        $this->set_content_type('application/json;charset=utf-8');
+        $this->response->add_header('Content-Length', strlen($json));
+        $this->render_text($json);
+    }
+
+    /**
+     * Render given data as csv, data is assumed to be utf-8.
+     * The first row of data may contain column titles.
+     *
+     * @param array $data       data as two dimensional array
+     * @param string $filename  download file name (optional)
+     * @param string $delimiter field delimiter char (optional)
+     * @param string $enclosure field enclosure char (optional)
+     */
+    public function render_csv($data, $filename = null, $delimiter = ';', $enclosure = '"')
+    {
+        $this->set_content_type('text/csv; charset=UTF-8');
+
+        $output = fopen('php://temp', 'rw');
+        fputs($output, "\xEF\xBB\xBF");
+
+        foreach ($data as $row) {
+            fputcsv($output, $row, $delimiter, $enclosure);
+        }
+
+        rewind($output);
+        $csv_data = stream_get_contents($output);
+        fclose($output);
+
+        if (isset($filename)) {
+            $this->response->add_header('Content-Disposition', 'attachment; ' . encode_header_parameter('filename', $filename));
+        }
+
+        $this->response->add_header('Content-Length', strlen($csv_data));
+
+        $this->render_text($csv_data);
+    }
+
+    /**
+     * Renders a pdf file given by a TCPDF/ExportPDF object.
+     *
+     * @param TCPDF   $pdf      TCPDF object to render
+     * @param string  $filename Filename
+     * @param bool    $inline   Should the pdf be displayed inline (default: no)
+     */
+    protected function render_pdf(TCPDF $pdf, $filename, $inline = false)
+    {
+        $temp_file = $GLOBALS['TMP_PATH'] . '/' . md5(uniqid('pdf-file', true));
+        $pdf->Output($temp_file, 'F');
+
+        $disposition = $inline ? 'inline' : 'attachment';
+
+        $this->render_temporary_file($temp_file, $filename, 'application/pdf', $disposition);
+    }
+
+    /**
+     * Renders a file
+     * @param string  $file                Path of the file to render
+     * @param string  $filename            Name of the file displayed to user
+     *                                     (will equal $file when missing)
+     * @param string  $content_type        Optional content type (will be determined if missing)
+     * @param string  $content_disposition Either attachment (default) or inline
+     * @param Closure $callback            Optional callback when download has finished
+     * @param int     $chunk_size          Optional size of chunks to send (default: 256k)
+     */
+    public function render_file(
+        $file,
+        $filename = null,
+        $content_type = null,
+        $content_disposition = 'attachment',
+        Closure $callback = null,
+        $chunk_size = 262144
+    ) {
+        if (!file_exists($file)) {
+            throw new Trails\Exception(404);
+        }
+
+        if (!is_readable($file)) {
+            throw new Trails\Exception(500);
+        }
+
+        if ($content_type === null) {
+            $content_type = get_mime_type($filename ?: $file);
+        }
+
+        if (!in_array($content_type, get_mime_types())) {
+            $content_type = 'application/octet-stream';
+        }
+
+        if ($content_type === 'application/octet-stream') {
+            $content_disposition = 'attachment';
+        }
+
+        $this->set_content_type($content_type);
+        $this->response->add_header(
+            'Content-Disposition',
+            "{$content_disposition}; " . encode_header_parameter(
+                'filename',
+                FileManager::cleanFileName($filename ?: basename($file))
+            )
+        );
+        $this->response->add_header('Content-Length', filesize($file));
+        $this->response->add_header('Content-Transfer-Encoding',  'binary');
+        $this->response->add_header('Pragma', 'public');
+        $this->render_text(function () use ($file, $chunk_size, $callback) {
+            $fp = fopen($file, 'rb');
+
+            while (!feof($fp)) {
+                yield fgets($fp, $chunk_size);
+            }
+
+            fclose($fp);
+
+            if ($callback) {
+                $callback($file);
+            }
+        });
+    }
+
+    /**
+     * Renders a temporary file which will be deleted after transmission.
+     * This is just a convenience method so you don't have to write the delete
+     * callback.
+     *
+     * @param string  $file                Path of the file to render
+     * @param string  $filename            Name of the file displayed to user
+     *                                     (will equal $file when missing)
+     * @param string  $content_type        Optional content type (will be determined if missing)
+     * @param string  $content_disposition Either attachment (default) or inline
+     * @param Closure $callback            Optional callback when download has finished
+     * @param int     $chunk_size          Optional size of chunks to send (default: 256k)
+     */
+    public function render_temporary_file(
+        $file,
+        $filename = null,
+        $content_type = null,
+        $content_disposition = 'attachment',
+        Closure $callback = null,
+        $chunk_size = 262144
+
+    ) {
+        $delete_callback = function ($file) use ($callback) {
+            unlink($file);
+
+            if ($callback) {
+                $callback($file);
+            }
+        };
+
+        $this->render_file(
+            $file,
+            $filename,
+            $content_type,
+            $content_disposition,
+            $delete_callback,
+            $chunk_size
+        );
+    }
+
+    public function render_form(\Studip\Forms\Form $form)
+    {
+        $this->render_text($form->render());
+    }
+
+    /**
+     * relays current request to another controller and returns the response
+     * the other controller is given all assigned properties, additional parameters are passed
+     * through
+     *
+     * @param string $to_uri a trails route
+     * @return Trails\Response
+     */
+    public function relay($to_uri/* , ... */)
+    {
+        $args = func_get_args();
+        $uri = array_shift($args);
+        [$controller_path, $unconsumed] = '' === $uri ? $this->dispatcher->default_route() : $this->dispatcher->parse($uri);
+
+        $controller = $this->dispatcher->load_controller($controller_path);
+        $assigns = $this->get_assigned_variables();
+        unset($assigns['controller']);
+        foreach ($assigns as $k => $v) {
+            $controller->$k = $v;
+        }
+        $controller->layout = null;
+        $controller->parent_controller = $this;
+        array_unshift($args, $unconsumed);
+        return $controller->perform_relayed(...$args);
+    }
+
+    /**
+     * Relays current request and performs redirect if neccessary.
+     *
+     * @param string $to_uri a trails route
+     * @return Trails\Response
+     *
+     * @see StudipController::relay()
+     */
+    public function relayWithRedirect(...$args): Trails\Response
+    {
+        $response = $this->relay(...$args);
+
+        // If the relayed action should perform a redirect, do so
+        if (isset($response->headers['Location'])) {
+            header("Location: {$response->headers['Location']}");
+            page_close();
+            die;
+        }
+
+        return $response;
+    }
+
+    /**
+     * perform a given action/parameter string from an relayed request
+     * before_filter and after_filter methods are not called
+     *
+     * @see perform
+     * @param string $unconsumed
+     * @return Trails\Response
+     */
+    public function perform_relayed($unconsumed/* , ... */)
+    {
+        $args = func_get_args();
+        $unconsumed = array_shift($args);
+
+        [$action, $extracted_args] = $this->extract_action_and_args($unconsumed);
+        $this->current_action = $action;
+        $args = array_merge($extracted_args, $args);
+        $callable = $this->map_action($action);
+
+        if (is_callable($callable)) {
+            $callable(...$args);
+        } else {
+            $this->does_not_understand($action, $args);
+        }
+
+        if (!$this->performed) {
+            $this->render_action($action);
+        }
+        return $this->response;
+    }
+
+    public function render_template($template_name, $layout = null)
+    {
+        if (Studip\Debug\DebugBar::isActivated()) {
+            $debugbar = app()->get(Debugbar::class);
+            if (!isset($debugbar['trails'])) {
+                $collector = new \Studip\Debug\TrailsCollector($this);
+                $debugbar->addCollector($collector);
+            }
+        }
+
+        parent::render_template($template_name, $layout);
+    }
+
+    /**
+     * Renders a given template and returns the resulting string.
+     *
+     * @param string $template Name of the template file
+     * @param mixed  $layout   Optional layout
+     * @return string
+     */
+    public function render_template_as_string($template, $layout = null)
+    {
+        $template = $this->get_template_factory()->open($template);
+        $template->set_layout($layout);
+        $template->set_attributes($this->get_assigned_variables());
+        return $template->render();
+    }
+
+    /**
+     * Magic methods that intercepts all unknown method calls.
+     * If a method is called that matches an action on this controller,
+     * an url to that action is generated.
+     *
+     * Basically, this:
+     *
+     *    <code>$controller->url_for('foo/bar/baz/' . $param)</code>
+     *
+     * is equal to calling this on the Foo_BarController:
+     *
+     *    <code>$controller->baz($param)</code>
+     *
+     * @param String $method    Called method name
+     * @param array  $arguments Provided arguments
+     * @return string url to the requested action
+     * @throws Trails\Exceptions\UnknownAction if no action matches the method
+     */
+    public function __call($method, $arguments)
+    {
+        $function = 'action_link';
+        if (mb_strpos($method, 'Link') === mb_strlen($method) - 4) {
+            $method = mb_substr($method, 0, -4);
+        } elseif (mb_strpos($method, 'URL') === mb_strlen($method) - 3) {
+            $function = 'action_url';
+            $method = mb_substr($method, 0, -3);
+        }
+
+        if (!$this->has_action($method)) {
+            throw new Trails\Exceptions\UnknownAction("Unknown action '{$method}'");
+        }
+
+        array_unshift($arguments, $method);
+        return call_user_func_array([$this, $function], $arguments);
+    }
+
+    /**
+     * Returns whether this controller has the specificed action.
+     *
+     * @param string $action Name of the action
+     * @return true if action is defined, false otherwise
+     */
+    public function has_action($action)
+    {
+        return method_exists($this, $action . '_action')
+            || ($this->parent_controller
+                && $this->parent_controller->has_action($action));
+    }
+
+    /**
+     * Generates the url for an action on this controller without the
+     * neccessity to provide the full "path" to the action (since it
+     * is implicitely known).
+     *
+     * Basically, this:
+     *
+     *    <code>$controller->url_for('foo/bar/baz/' . $param)</code>
+     *
+     * is equal to calling this on the Foo_BarController:
+     *
+     *    <code>$controller->action_url('baz/' . $param)</code>
+     *
+     * @param string $action Name of the action
+     * @return string url to the requested action
+     */
+    public function action_url($action)
+    {
+        $arguments = func_get_args();
+        $arguments[0] = $this->controller_path() . '/' . $arguments[0];
+
+        return $this->url_for(...$arguments);
+    }
+
+    /**
+     * Generates the link for an action on this controller without the
+     * neccessity to provide the full "path" to the action (since it
+     * is implicitely known).
+     *
+     * Basically, this:
+     *
+     *    <code>$controller->link_for('foo/bar/baz/' . $param)</code>
+     *
+     * is equal to calling this on the Foo_BarController:
+     *
+     *    <code>$controller->action_link('baz/' . $param)</code>
+     *
+     * @param string $action Name of the action
+     * @return string to the requested action
+     */
+    public function action_link($action)
+    {
+        return htmlReady($this->action_url(...func_get_args()));
+    }
+
+    /**
+     * Returns the url path to this controller.
+     *
+     * @return string url path to this controller
+     */
+    protected function controller_path()
+    {
+        $class = get_class($this->parent_controller ?? $this);
+        $controller = mb_substr($class, 0, -mb_strlen('Controller'));
+        $controller = strtosnakecase($controller);
+        return preg_replace('/_{2,}/', '/', $controller);
+    }
+
+
+    /**
+     * Validate the datetime according to specific format.
+     *
+     * @param string $datetime the datetime which should be validate
+     * @param string $format the format that the datetime should have by default H:i for time
+     *
+     * @return bool result of validation
+     */
+    public function validate_datetime($datetime, $format = 'H:i')
+    {
+        $dt = DateTime::createFromFormat($format, $datetime);
+        return $dt && $dt->format($format) == date('H:i',strtotime($datetime));
+    }
+
+    /**
+     * Export xlsx and csv files via PhpSpreadsheet
+     *
+     * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
+     */
+    public function render_spreadsheet(
+        array $header,
+        array $data,
+        string $format,
+        string $filename,
+        ?string $filepath = null
+    ): void  {
+        $render_to_browser = false;
+        if ($filepath == null) {
+            $render_to_browser = true;
+            $filepath = tempnam($GLOBALS['TMP_PATH'], 'spreadsheet');
+        }
+        $spreadsheet = new Spreadsheet();
+        $activeWorksheet = $spreadsheet->getActiveSheet();
+        $activeWorksheet->fromArray($header);
+        $activeWorksheet->fromArray($data, null, 'A2');
+
+        if ($format === 'xlsx') {
+            $writer = new Xlsx($spreadsheet);
+        } elseif ($format === 'csv') {
+            $writer = new Csv($spreadsheet);
+        } else {
+            throw new Exception("Format {$format} is not supported");
+        }
+
+        $writer->save($filepath);
+
+        if ($render_to_browser) {
+            $this->response->add_header('Cache-Control', 'cache, must-revalidate');
+            $this->render_temporary_file(
+                $filepath,
+                $filename,
+                'application/vnd.openxmlformats-officedocument.spreadsheetml.sheet'
+            );
+        }
+    }
+
+    /**
+     * Creates the body element id for this controller a given action.
+     *
+     * @param string $unconsumed_path Unconsumed path to extract action from
+     * @return string
+     */
+    protected function getBodyElementIdForControllerAndAction($unconsumed_path)
+    {
+        // Extract action from unconsumed path segment
+        [$action] = $this->extract_action_and_args($unconsumed_path);
+
+        // Extract controller name from class name
+        $controller = preg_replace('/Controller$/', '', get_class($this));
+        $controller = Trails\Inflector::underscore($controller);
+
+        // Build main parts of the body element id
+        $body_id_parts = explode('/', $controller);
+        $body_id_parts[] = $action;
+
+        // Create and set body element id
+        $body_id = implode('-', $body_id_parts);
+
+        return $body_id;
+    }
+}
diff --git a/lib/classes/StudipControllerPropertiesTrait.php b/lib/classes/StudipControllerPropertiesTrait.php
new file mode 100644
index 0000000..4e906fa
--- /dev/null
+++ b/lib/classes/StudipControllerPropertiesTrait.php
@@ -0,0 +1,69 @@
+<?php
+/**
+ * This trait manages all variable assignments to the controller and templates.
+ *
+ * @author Jan-Hendrik Willms <tleilax+studip@gmail.com>
+ * @license GPL2 or any later version
+ * @since Stud.IP 5.2
+ */
+trait StudipControllerPropertiesTrait
+{
+    /**
+     * Stores the assigned variables.
+     * @var array
+     */
+    protected $_template_variables = [];
+
+    /**
+     * Returns whether a variable is set.
+     *
+     * @param string $offset
+     * @return bool
+     */
+    public function __isset(string $offset): bool
+    {
+        return isset($this->_template_variables[$offset]);
+    }
+
+    /**
+     * Stores a variable.
+     *
+     * @param string $offset
+     * @param mixed $value
+     */
+    public function __set(string $offset, $value): void
+    {
+        $this->_template_variables[$offset] = $value;
+    }
+
+    /**
+     * Returns a previously set variable.
+     *
+     * @param string $offset
+     * @return mixed
+     */
+    public function &__get(string $offset)
+    {
+        if (!isset($this->_template_variables[$offset])) {
+            $this->_template_variables[$offset] = null;
+        }
+        return $this->_template_variables[$offset];
+    }
+
+    /**
+     * Unsets a previously set variable
+     *
+     * @param string $offset
+     */
+    public function __unset(string $offset): void
+    {
+        unset($this->_template_variables[$offset]);
+    }
+
+    public function get_assigned_variables(): array
+    {
+        $variables = $this->_template_variables;
+        $variables['controller'] = $this;
+        return $variables;
+    }
+}
diff --git a/lib/classes/StudipCoreFormat.php b/lib/classes/StudipCoreFormat.php
index 24c4ddc..7e3358c 100644
--- a/lib/classes/StudipCoreFormat.php
+++ b/lib/classes/StudipCoreFormat.php
@@ -605,11 +605,6 @@ class StudipCoreFormat extends TextFormat
             $title
         );
 
-        if ($tag === 'audio') {
-            $random_id = 'audio-' . mb_substr(md5(uniqid('audio', true)), -8);
-            $media = str_replace('<audio ', '<audio id="' . $random_id . '" onerror="STUDIP.Audio.handle(this);" ', $media);
-        }
-
         if ($link && $tag === "img") {
             $media = sprintf('<a href="%s"%s>%s</a>',
                 $link,
diff --git a/lib/classes/StudipDbCache.class.php b/lib/classes/StudipDbCache.class.php
deleted file mode 100644
index 865825e..0000000
--- a/lib/classes/StudipDbCache.class.php
+++ /dev/null
@@ -1,123 +0,0 @@
-<?php
-/**
- * StudipCache implementation using database table
- *
- * @package     studip
- * @subpackage  cache
- *
- * @author    Elmar Ludwig <elmar.ludwig@uos.de>
- */
-class StudipDbCache implements StudipCache
-{
-
-    /**
-     * @return string A translateable display name for this cache class.
-     */
-    public static function getDisplayName(): string
-    {
-        return _('Datenbank');
-    }
-
-    /**
-     * Expire item from the cache.
-     *
-     * @param string $arg a single key
-     */
-    public function expire($arg)
-    {
-        $db = DBManager::get();
-
-        $stmt = $db->prepare('DELETE FROM cache WHERE cache_key = ?');
-        $stmt->execute([$arg]);
-    }
-
-    /**
-     * Expire all items from the cache.
-     */
-    public function flush()
-    {
-        $db = DBManager::get();
-
-        $db->exec('TRUNCATE TABLE cache');
-    }
-
-    /**
-     * Delete all expired items from the cache.
-     */
-    public function purge()
-    {
-        $db = DBManager::get();
-
-        $stmt = $db->prepare('DELETE FROM cache WHERE expires < ?');
-        $stmt->execute([time()]);
-    }
-
-    /**
-     * Retrieve item from the server.
-     *
-     * @param string $arg a single key
-     *
-     * @return mixed    the previously stored data if an item with such a key
-     *                  exists on the server or FALSE on failure.
-     */
-    public function read($arg)
-    {
-        $db = DBManager::get();
-
-        $stmt = $db->prepare('SELECT content FROM cache WHERE cache_key = ? AND expires > ?');
-        $stmt->execute([$arg, time()]);
-        $result = $stmt->fetchColumn();
-
-        return $result !== false ? unserialize($result) : false;
-    }
-
-    /**
-     * Store data at the server.
-     *
-     * @param string $name     the item's key.
-     * @param mixed  $content  the item's content (will be serialized if necessary).
-     * @param int    $expired  the item's expiry time in seconds. Optional, defaults to 12h.
-     *
-     * @return bool     returns TRUE on success or FALSE on failure.
-     */
-    public function write($name, $content, $expires = self::DEFAULT_EXPIRATION)
-    {
-        $db = DBManager::get();
-
-        $stmt = $db->prepare('REPLACE INTO cache VALUES(?, ?, ?)');
-        return $stmt->execute([$name, serialize($content), time() + $expires]);
-    }
-
-    /**
-     * Return statistics.
-     *
-     * @see StudipCache::getStats()
-     *
-     * @return array|array[]
-     */
-    public function getStats(): array
-    {
-        return [
-            __CLASS__ => [
-                'name' => _('Anzahl Einträge'),
-                'value' => DBManager::get()->fetchColumn("SELECT COUNT(*) FROM `cache`")
-            ]
-        ];
-    }
-
-    /**
-     * Return the Vue component name and props that handle configuration.
-     *
-     * @see StudipCache::getConfig()
-     *
-     * @return array
-     */
-    public static function getConfig(): array
-    {
-        return [
-            'component' => null,
-            'props' => []
-        ];
-    }
-
-}
diff --git a/lib/classes/StudipDispatcher.php b/lib/classes/StudipDispatcher.php
index af0ea48..a41635a 100644
--- a/lib/classes/StudipDispatcher.php
+++ b/lib/classes/StudipDispatcher.php
@@ -18,29 +18,31 @@ use Psr\Container\ContainerInterface;
 
 /**
  * Use this subclass to easily get an Stud.IP specific
- * Trails_Dispatcher.
+ * Trails\Dispatcher.
  *
  * Example of use:
+ *
  * @code
  * // deep in the Stud.IP jungle
  * $dispatcher = new StudipDispatcher();
  * $dispatcher->dispatch($requested_uri);
  * @endcode
  */
-class StudipDispatcher extends Trails_Dispatcher {
-
-  /**
-   * This variable contains the DI-Container.
-   * @var ContainerInterface
-   */
-  protected $container;
+class StudipDispatcher extends Trails\Dispatcher
+{
+    /**
+     * This variable contains the DI-Container.
+     *
+     * @var ContainerInterface
+     */
+    protected $container;
 
-  /**
-   * Create a new Trails_Dispatcher with Stud.IP specific parameters
-   * for: trails_root is "$STUDIP_BASE_PATH/app", trails_uri is
-   * "dispatch.php" and default_controller is "default" (which does
-   * not map to anything).
-   */
+    /**
+     * Create a new Trails\Dispatcher with Stud.IP specific parameters
+     * for: trails_root is "$STUDIP_BASE_PATH/app", trails_uri is
+     * "dispatch.php" and default_controller is "default" (which does
+     * not map to anything).
+     */
     public function __construct(ContainerInterface $container)
     {
         global $STUDIP_BASE_PATH, $ABSOLUTE_URI_STUDIP;
@@ -58,6 +60,7 @@ class StudipDispatcher extends Trails_Dispatcher {
      * exception instead of the standard trails handling.
      *
      * @param Exception $exception The exception that occured
+     *
      * @throws Exception
      */
     public function trails_error($exception)
@@ -66,21 +69,22 @@ class StudipDispatcher extends Trails_Dispatcher {
     }
 
     /**
-   * Loads the controller file for a given controller path and return an
-   * instance of that controller. If an error occures, an exception will be
-   * thrown.
-   *
-   * @param  string            the relative controller path
-   *
-   * @return TrailsController  an instance of that controller
-   */
-  function load_controller($controller) {
-    require_once "{$this->trails_root}/controllers/{$controller}.php";
-    $class = Trails_Inflector::camelize($controller) . 'Controller';
-    if (!class_exists($class)) {
-      throw new Trails_UnknownController("Controller missing: '$class'");
-    }
+     * Loads the controller file for a given controller path and return an
+     * instance of that controller. If an error occures, an exception will be
+     * thrown.
+     *
+     * @param string $controller the relative controller path
+     * @return Trails\Controller  an instance of that controller
+     * @throws \Trails\Exceptions\UnknownController
+     */
+    public function load_controller($controller)
+    {
+        require_once "{$this->trails_root}/controllers/{$controller}.php";
+        $class = Trails\Inflector::camelize($controller) . 'Controller';
+        if (!class_exists($class)) {
+            throw new Trails\Exceptions\UnknownController("Controller missing: '$class'");
+        }
 
-    return $this->container->make($class, ['dispatcher' => $this]);
-  }
+        return $this->container->make($class, ['dispatcher' => $this]);
+    }
 }
diff --git a/lib/classes/StudipFileloader.php b/lib/classes/StudipFileloader.php
index f499b68..aab0b31 100644
--- a/lib/classes/StudipFileloader.php
+++ b/lib/classes/StudipFileloader.php
@@ -27,6 +27,12 @@ class StudipFileloader
         $_oldVariableNames = array_keys(get_defined_vars());
 
         foreach (preg_split('/ /', $_filename, -1, PREG_SPLIT_NO_EMPTY) as $file) {
+            if (
+                !file_exists($file)
+                && !stream_resolve_include_path($file)
+            ) {
+                throw new Exception('Missing file '. $file);
+            }
             include $file;
         }
         unset($file);
diff --git a/lib/classes/StudipForm.class.php b/lib/classes/StudipForm.php
index 024e2e3..12029df 100644
--- a/lib/classes/StudipForm.class.php
+++ b/lib/classes/StudipForm.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipForm.class.php
+// StudipForm.php
 // Class to build HTML formular and handle persistence using PhpLib
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipItem.interface.php b/lib/classes/StudipItem.php
index b575bdc..b575bdc 100644
--- a/lib/classes/StudipItem.interface.php
+++ b/lib/classes/StudipItem.php
diff --git a/lib/classes/StudipKing.class.php b/lib/classes/StudipKing.php
index 2d1f15c..ae5a14e 100644
--- a/lib/classes/StudipKing.class.php
+++ b/lib/classes/StudipKing.php
@@ -63,7 +63,7 @@ class StudipKing {
     private static function get_kings()
     {
         if (self::$kings === null) {
-            $cache = StudipCacheFactory::getCache();
+            $cache = \Studip\Cache\Factory::getCache();
 
             # read cache (unserializing a cache miss - FALSE - does not matter)
             $kings = unserialize($cache->read(self::CACHE_KEY));
@@ -118,7 +118,7 @@ class StudipKing {
         $kings = [];
 
         // sum up postings for all users from all ForumModules available
-        foreach (PluginEngine::getPlugins('ForumModule') as $plugin) {
+        foreach (PluginEngine::getPlugins(ForumModule::class) as $plugin) {
             $table = $plugin->getEntryTableInfo();
             $query = "SELECT user_id AS id, COUNT(*) AS num FROM ". $table['table'] ." GROUP BY user_id";
             $new_kings = self::select_kings($query);
diff --git a/lib/classes/StudipLink.class.php b/lib/classes/StudipLink.php
index b4e80ba..b4e80ba 100644
--- a/lib/classes/StudipLink.class.php
+++ b/lib/classes/StudipLink.php
diff --git a/lib/classes/StudipLock.class.php b/lib/classes/StudipLock.php
index 601db8b..ce5752f 100644
--- a/lib/classes/StudipLock.class.php
+++ b/lib/classes/StudipLock.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * StudipLock.class.php
+ * StudipLock.php
  * class with methods to perform cooperative advisory locking
  * using the GET_LOCK feature from Mysql
  * https://dev.mysql.com/doc/refman/5.0/en/miscellaneous-functions.html#function_get-lock
diff --git a/lib/classes/StudipLog.class.php b/lib/classes/StudipLog.php
index 7a520c9..7a520c9 100644
--- a/lib/classes/StudipLog.class.php
+++ b/lib/classes/StudipLog.php
diff --git a/lib/classes/StudipLvgruppeSelection.class.php b/lib/classes/StudipLvgruppeSelection.php
index a5da9cb..a5da9cb 100644
--- a/lib/classes/StudipLvgruppeSelection.class.php
+++ b/lib/classes/StudipLvgruppeSelection.php
diff --git a/lib/classes/StudipMail.class.php b/lib/classes/StudipMail.php
index db68a11..c517847 100644
--- a/lib/classes/StudipMail.class.php
+++ b/lib/classes/StudipMail.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * StudipMail.class.php
+ * StudipMail.php
  *
  * class for constructing and sending emails in Stud.IP
  *
@@ -36,6 +36,11 @@ class StudipMail
      */
     private $attachments = [];
     /**
+     * Array of attachments that are related to the content
+     * @var array
+     */
+    private $related_attachments = [];
+    /**
      * @var array
      */
     private $sender;
@@ -307,6 +312,17 @@ class StudipMail
         return $this;
     }
 
+    public function addRelatedAttachment(string $file_name, string $name, string $type, string $content_id): void
+    {
+        $this->related_attachments[$name] = [
+            'FileName' => $file_name,
+            'Name' => $name,
+            'Content-Type' => $type,
+            'Disposition' => 'inline',
+            'Content-ID' => $content_id
+        ];
+    }
+
     /**
      * @param $name
      * @return StudipMail provides fluent interface
@@ -411,16 +427,29 @@ class StudipMail
             $transporter->SetMultipleEncodedEmailHeader($type, $recipients);
         }
         $transporter->SetEncodedHeader('Subject', $this->getSubject());
-        if($this->getBodyHtml()){
-            $html_part = '';
+        if($this->getBodyHtml()) {
+            $html_part = 0;
             $transporter->CreateQuotedPrintableHTMLPart($this->getBodyHtml(), "", $html_part);
             $text_part = '';
             $text_message = $this->getBodyText();
+
             if(!$text_message){
                 $text_message = _('Diese Nachricht ist im HTML-Format verfasst. Sie benötigen eine E-Mail-Anwendung, die das HTML-Format anzeigen kann.');
             }
             $transporter->CreateQuotedPrintableTextPart($transporter->WrapText($text_message), "", $text_part);
+
             $part = [$text_part, $html_part];
+            if (count($this->related_attachments) > 0) {
+                $relparts = [$html_part];
+                $i = 99;
+                $multipart = 0;
+                foreach ($this->related_attachments as $one) {
+                    $transporter->CreateFilePart($one, $i);
+                    $relparts[] = $i;
+                }
+                $transporter->CreateRelatedMultipart($relparts, $multipart);
+                $part = [$text_part, $multipart];
+            }
             $transporter->AddAlternativeMultipart($part);
         } else {
             $transporter->AddQuotedPrintableTextPart($this->getBodyText());
diff --git a/lib/classes/StudipMemoryCache.class.php b/lib/classes/StudipMemoryCache.class.php
deleted file mode 100644
index d38385a..0000000
--- a/lib/classes/StudipMemoryCache.class.php
+++ /dev/null
@@ -1,84 +0,0 @@
-<?php
-/**
- * The php memory implementation of the StudipCache interface.
- *
- * @author  Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @license GPL2 or any later version
- * @since   Stud.IP 5.0
- */
-class StudipMemoryCache implements StudipCache
-{
-    protected $memory_cache = [];
-
-    /**
-     * Expires just a single key.
-     *
-     * @param  string  the key
-     */
-    public function expire($key)
-    {
-        unset($this->memory_cache[$key]);
-    }
-
-    /**
-     * Expire all items from the cache.
-     */
-    public function flush()
-    {
-        $this->memory_cache = [];
-    }
-
-    /**
-     * Reads just a single key from the cache.
-     *
-     * @param  string  the key
-     *
-     * @return mixed   the corresponding value
-     */
-    public function read($key)
-    {
-        if (!isset($this->memory_cache[$key])) {
-            return false;
-        }
-        if ($this->memory_cache[$key]['expires'] < time()) {
-            $this->expire($key);
-            return false;
-        }
-        return $this->memory_cache[$key]['data'];
-    }
-
-    /**
-     * Store data at the server.
-     *
-     * @param string   the item's key.
-     * @param mixed    the item's content (will be serialized if necessary).
-     * @param int      the item's expiry time in seconds. Defaults to 12h.
-     *
-     * @returns mixed  returns TRUE on success or FALSE on failure.
-     *
-     */
-    public function write($name, $content, $expires = self::DEFAULT_EXPIRATION)
-    {
-        $this->memory_cache[$name] = [
-            'expires' => time() + $expires,
-            'data'    => $content,
-        ];
-
-        return true;
-    }
-
-    public static function getDisplayName(): string
-    {
-        return 'Memory cache';
-    }
-
-    public function getStats(): array
-    {
-        return [];
-    }
-
-    public static function getConfig(): array
-    {
-        return [];
-    }
-}
diff --git a/lib/classes/StudipObject.class.php b/lib/classes/StudipObject.php
index 151fcdb..5f10c86 100644
--- a/lib/classes/StudipObject.class.php
+++ b/lib/classes/StudipObject.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +--------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipObject.class.php
+// StudipObject.php
 //
 // Class to provide basic properties of an StudipObject in Stud.IP
 //
@@ -36,7 +36,7 @@ define ("INSTANCEOF_STUDIPOBJECT", "StudipObject");
 
 
 /**
- * StudipObject.class.php
+ * StudipObject.php
  *
  * Class to provide basic properties of an StudipObject in Stud.IP
  *
diff --git a/lib/classes/StudipPDO.class.php b/lib/classes/StudipPDO.php
index e77a37f..77046f7 100644
--- a/lib/classes/StudipPDO.class.php
+++ b/lib/classes/StudipPDO.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * StudipPDO.class.php - Stud.IP PDO class
+ * StudipPDO.php - Stud.IP PDO class
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -23,7 +23,6 @@ class StudipPDO extends PDO
 
     // Counter for the queries sent to the database
     public $query_count = 0;
-    public $queries     = [];
 
     /**
      * Verifies that the given SQL query only contains a single statement.
@@ -42,26 +41,6 @@ class StudipPDO extends PDO
         // Count executed queries (this is placed here since this is the only
         // method that is executed on every call to the database)
         $this->query_count += 1;
-
-        if (!empty($GLOBALS['DEBUG_ALL_DB_QUERIES'])) {
-            $trace = debug_backtrace();
-
-            $classes = [];
-            if (isset($trace[2]['class']) && $trace[2]['class'] === 'SimpleORMap') {
-                $classes[] = 'sorm';
-            }
-            if (isset($trace[1]) && $trace[1]['function'] === 'prepare') {
-                $classes[] = 'prepared';
-            }
-
-            $this->queries[] = [
-                'query'   => implode("\n", array_filter(array_map('trim', explode("\n", $statement)))),
-                'classes' => implode(' ', $classes),
-                'trace'   => $GLOBALS['DEBUG_ALL_DB_QUERIES_WITH_TRACE']
-                           ? array_slice($trace, 2)
-                           : null,
-            ];
-        }
     }
 
     /**
@@ -122,23 +101,20 @@ class StudipPDO extends PDO
      * Quotes the given value in a form appropriate for the type.
      * If no explicit type is given, the value's PHP type is used.
      *
-     * @param mixed $value PHP value to quote
+     * @param mixed $string PHP value to quote
      * @param ?int $type parameter type (e.g. PDO::PARAM_STR)
      * @return string|false quoted SQL string
-     *
-     * @todo Add string|false return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function quote($value, $type = null)
+    public function quote($string, $type = null): false|string
     {
         if (!isset($type)) {
-            if (is_null($value)) {
+            if (is_null($string)) {
                 $type = PDO::PARAM_NULL;
-            } else if (is_bool($value)) {
+            } else if (is_bool($string)) {
                 $type = PDO::PARAM_BOOL;
-            } else if (is_int($value)) {
+            } else if (is_int($string)) {
                 $type = PDO::PARAM_INT;
-            } else if (is_array($value)) {
+            } else if (is_array($string)) {
                 $type = StudipPDO::PARAM_ARRAY;
             } else {
                 $type = PDO::PARAM_STR;
@@ -149,28 +125,24 @@ class StudipPDO extends PDO
             case PDO::PARAM_NULL:
                 return 'NULL';
             case PDO::PARAM_BOOL:
-                return $value ? '1' : '0';
+                return $string ? '1' : '0';
             case PDO::PARAM_INT:
-                return (int) $value;
+                return (int) $string;
             case StudipPDO::PARAM_ARRAY:
-                return is_array($value) && count($value) ? join(',', array_map([$this, 'quote'], $value)) : 'NULL';
+                return is_array($string) && count($string) ? join(',', array_map([$this, 'quote'], $string)) : 'NULL';
             case StudipPDO::PARAM_COLUMN:
-                return preg_replace('/\\W/', '', $value);
+                return preg_replace('/\\W/', '', $string);
             default:
-                return parent::quote($value);
+                return parent::quote($string);
         }
     }
 
     /**
      * Executes an SQL statement and returns the number of affected rows.
      *
-     * @param string    SQL statement
-     * @return int|false      number of affected rows
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
+     * @param string $statement SQL statement
      */
-    #[ReturnTypeWillChange]
-    public function exec($statement)
+    public function exec(string $statement): false|int
     {
         $this->verify($statement);
         return parent::exec($statement);
diff --git a/lib/classes/StudipPDOStatement.php b/lib/classes/StudipPDOStatement.php
index 4a3d069..80a8dc8 100644
--- a/lib/classes/StudipPDOStatement.php
+++ b/lib/classes/StudipPDOStatement.php
@@ -99,11 +99,8 @@ class StudipPDOStatement implements IteratorAggregate
 
     /**
      * Forwards all Iterator methods to the actual statement object.
-     *
-     * @todo Add Traversable return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         return $this->stmt;
     }
diff --git a/lib/classes/StudipRangeTree.class.php b/lib/classes/StudipRangeTree.php
index cf88d23..5e1aefe 100644
--- a/lib/classes/StudipRangeTree.class.php
+++ b/lib/classes/StudipRangeTree.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipRangeTree.class.php
+// StudipRangeTree.php
 // Class to handle structure of the "range tree"
 //
 // Copyright (c) 2002 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipRangeTreeView.class.php b/lib/classes/StudipRangeTreeView.php
index 2532e4b..7b23089 100644
--- a/lib/classes/StudipRangeTreeView.class.php
+++ b/lib/classes/StudipRangeTreeView.php
@@ -6,7 +6,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipRangeTreeView.class.php
+// StudipRangeTreeView.php
 // Class to print out the "range tree"
 //
 // Copyright (c) 2002 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipRangeTreeViewAdmin.class.php b/lib/classes/StudipRangeTreeViewAdmin.php
index 0620957..1c5e5a1 100644
--- a/lib/classes/StudipRangeTreeViewAdmin.class.php
+++ b/lib/classes/StudipRangeTreeViewAdmin.php
@@ -6,7 +6,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipRangeTreeViewAdmin.class.php
+// StudipRangeTreeViewAdmin.php
 // Class to print out the "range tree"
 //
 // Copyright (c) 2002 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipResponse.php b/lib/classes/StudipResponse.php
new file mode 100644
index 0000000..a9f1a4c
--- /dev/null
+++ b/lib/classes/StudipResponse.php
@@ -0,0 +1,55 @@
+<?php
+class StudipResponse extends Trails\Response
+{
+    /**
+     * Outputs this response to the client using "echo" and "header".
+     *
+     * This extension allows the body to be a callable and handles generators
+     * by outputting the chunks yielded by the generator.
+     */
+    public function output()
+    {
+        if (isset($this->status)) {
+            $this->send_header(
+                "{$_SERVER['SERVER_PROTOCOL']} {$this->status} {$this->reason}",
+                true,
+                $this->status
+            );
+        }
+
+        // Send headers
+        foreach ($this->headers as $k => $v) {
+            $this->send_header("{$k}: {$v}");
+        }
+
+        // Determine output
+        if (is_callable($this->body)) {
+            $output = call_user_func($this->body);
+        } else {
+            $output = $this->body;
+        }
+
+        if ($output instanceof Generator) {
+            // Clear output buffer
+            while (ob_get_level()) {
+                ob_end_clean();
+            }
+
+            // Ensure generator will run to the end
+            $abort = ignore_user_abort(true);
+
+            // Output chunks yielded by generator
+            foreach ($output as $chunk) {
+                if (!connection_aborted()) {
+                    echo $chunk;
+                    flush();
+                }
+            }
+
+            // Reset user abort to previous state
+            ignore_user_abort($abort);
+        } else {
+            echo $output;
+        }
+    }
+}
diff --git a/lib/classes/StudipSemRangeTreeViewSimple.class.php b/lib/classes/StudipSemRangeTreeViewSimple.php
index eecdd70..78b5ccf 100644
--- a/lib/classes/StudipSemRangeTreeViewSimple.class.php
+++ b/lib/classes/StudipSemRangeTreeViewSimple.php
@@ -6,7 +6,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipSemRangeTreeViewSimple.class.php
+// StudipSemRangeTreeViewSimple.php
 // Class to print out the seminar tree
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipSemSearch.class.php b/lib/classes/StudipSemSearch.php
index 8932dd1..6d86b44 100644
--- a/lib/classes/StudipSemSearch.class.php
+++ b/lib/classes/StudipSemSearch.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipSemSearchForm.class.php
+// StudipSemSearchForm.php
 // Class to build search formular and execute search
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipSemSearchHelper.class.php b/lib/classes/StudipSemSearchHelper.php
index 29ee5d3..d221869 100644
--- a/lib/classes/StudipSemSearchHelper.class.php
+++ b/lib/classes/StudipSemSearchHelper.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipSemSearchHelper.class.php
+// StudipSemSearchHelper.php
 //
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipSemTree.class.php b/lib/classes/StudipSemTree.php
index 70743ad..70743ad 100644
--- a/lib/classes/StudipSemTree.class.php
+++ b/lib/classes/StudipSemTree.php
diff --git a/lib/classes/StudipSemTreeSearch.class.php b/lib/classes/StudipSemTreeSearch.php
index e79a34f..0d8f935 100644
--- a/lib/classes/StudipSemTreeSearch.class.php
+++ b/lib/classes/StudipSemTreeSearch.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipSemTreeSearch.class.php
+// StudipSemTreeSearch.php
 // Class to build search formular and execute search
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipSemTreeView.class.php b/lib/classes/StudipSemTreeView.php
index 3e984cc..f2d6fbe 100644
--- a/lib/classes/StudipSemTreeView.class.php
+++ b/lib/classes/StudipSemTreeView.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipSemTreeView.class.php
+// StudipSemTreeView.php
 // Class to print out the seminar tree
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipSemTreeViewAdmin.class.php b/lib/classes/StudipSemTreeViewAdmin.php
index edc65c8..59c926a 100644
--- a/lib/classes/StudipSemTreeViewAdmin.class.php
+++ b/lib/classes/StudipSemTreeViewAdmin.php
@@ -7,7 +7,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipSemTreeViewAdmin.class.php
+// StudipSemTreeViewAdmin.php
 // Class to print out the seminar tree in administration mode
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipSemTreeViewSimple.class.php b/lib/classes/StudipSemTreeViewSimple.php
index e2dba76..239275b 100644
--- a/lib/classes/StudipSemTreeViewSimple.class.php
+++ b/lib/classes/StudipSemTreeViewSimple.php
@@ -6,7 +6,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipSemTreeViewSimple.class.php
+// StudipSemTreeViewSimple.php
 // Class to print out the seminar tree
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/StudipStudyAreaSelection.class.php b/lib/classes/StudipStudyAreaSelection.php
index ea2ea6f..ea2ea6f 100644
--- a/lib/classes/StudipStudyAreaSelection.class.php
+++ b/lib/classes/StudipStudyAreaSelection.php
diff --git a/lib/classes/StudipTransformFormat.php b/lib/classes/StudipTransformFormat.php
deleted file mode 100644
index 04cf7a3..0000000
--- a/lib/classes/StudipTransformFormat.php
+++ /dev/null
@@ -1,99 +0,0 @@
-<?php
-/**
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of
- * the License, or (at your option) any later version.
- *
- * @author      <mlunzena@uos.de
- * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
- * @category    Stud.IP
- */
-
-/**
- * Format class to transform text before it is saved into the database.
- * @deprecated since Stud.IP 5.3
- */
-class StudipTransformFormat extends TextFormat
-{
-    /**
-     * list of global Stud.IP transform markup rules
-     */
-    private static $studip_rules = [
-        'signature' => [
-            'start'    => '(?<!~)~~~(?!~)',
-            'callback' => 'StudipTransformFormat::markupSignature'
-        ]
-        ,'nop' => [
-            'start'    => '\[nop\](.*?)\[\/nop\]',
-            'callback' => 'StudipTransformFormat::markupNoFormat'
-        ],        
-    ];
-
-    /**
-     * Returns the list of global Stud.IP markup rules as an array.
-     * Each entry has the following attributes: 'start', 'end' and
-     * 'callback'. The rule name is used as the entry's array key.
-     *
-     * @return array list of all markup rules
-     */
-    public static function getStudipMarkups()
-    {
-        return self::$studip_rules;
-    }
-
-    /**
-     * Adds a new markup rule to the global Stud.IP markup set. This can
-     * also be used to replace an existing markup rule. The end regular
-     * expression is optional (i.e. may be NULL) to indicate that this
-     * rule has an empty content model. The callback is called whenever
-     * the rule matches and is passed the following arguments:
-     *
-     * - $markup    the markup parser object
-     * - $matches   match results of preg_match for $start
-     * - $contents  (parsed) contents of this markup rule
-     *
-     * @param string $name      name of this rule
-     * @param string $start     start regular expression
-     * @param string $end       end regular expression (optional)
-     * @param callback $callback function generating output of this rule
-     */
-    public static function addStudipMarkup($name, $start, $end, $callback)
-    {
-        self::$studip_rules[$name] = compact('start', 'end', 'callback');
-    }
-
-    /**
-     * Removes a markup rule from the global Stud.IP markup set.
-     *
-     * @param string $name      name of the rule
-     */
-    public static function removeStudipMarkup($name)
-    {
-        unset(self::$studip_rules[$name]);
-    }
-
-    /**
-     * Initializes a new StudipFormat instance.
-     */
-    public function __construct()
-    {
-        parent::__construct(self::getStudipMarkups());
-    }
-
-    /**
-     * Stud.IP markup for signatures
-     */
-    protected static function markupSignature($markup, $matches)
-    {
-        return get_fullname();
-    }
-
-    /**
-     * Stud.IP markup for unformatted text
-     */
-    protected static function markupNoFormat($markup, $matches)
-    {
-        return '[nop]' . $markup->quote($matches[1]) . '[/nop]';
-    }
-}
diff --git a/lib/classes/StudipTreeNodeCachableTrait.php b/lib/classes/StudipTreeNodeCachableTrait.php
index 31823ac..d40cf70 100644
--- a/lib/classes/StudipTreeNodeCachableTrait.php
+++ b/lib/classes/StudipTreeNodeCachableTrait.php
@@ -37,7 +37,7 @@ trait StudipTreeNodeCachableTrait
         return $config;
     }
 
-    protected function getDescendantIds(): array
+    public function getDescendantIds(): array
     {
         $cache = self::getDescendantsCacheArray();
 
diff --git a/lib/classes/StudygroupAvatar.class.php b/lib/classes/StudygroupAvatar.php
index 8e27f8e..8e27f8e 100644
--- a/lib/classes/StudygroupAvatar.class.php
+++ b/lib/classes/StudygroupAvatar.php
diff --git a/lib/classes/StudygroupModel.php b/lib/classes/StudygroupModel.php
index 76899f1..051ada7 100644
--- a/lib/classes/StudygroupModel.php
+++ b/lib/classes/StudygroupModel.php
@@ -532,7 +532,7 @@ class StudygroupModel
         if (StudygroupModel::isInvited($user_id, $sem_id)) {
             $subject .= ' ' . _('Einladung akzeptiert');
             $message = sprintf(
-                _("%s hat die Einladung zur Studiengruppe %s akzeptiert. Klicken Sie auf den untenstehenden Link, um direkt zur Studiengruppe zu gelangen.\n\n [Direkt zur Studiengruppe]%s"),
+                _("%s hat die Einladung zur Studiengruppe %s akzeptiert. Klicken Sie auf den folgenden Link, um direkt zur Studiengruppe zu gelangen.\n\n [Direkt zur Studiengruppe]%s"),
                 get_fullname($user_id),
                 $sem->getName(),
                 URLHelper::getlink(
@@ -543,7 +543,7 @@ class StudygroupModel
         } else {
             $subject .= ' ' . _('Neuer Mitgliedsantrag');
             $message = sprintf(
-                _("%s möchte der Studiengruppe %s beitreten. Klicken Sie auf den untenstehenden Link, um direkt zur Studiengruppe zu gelangen.\n\n [Direkt zur Studiengruppe]%s"),
+                _("%s möchte der Studiengruppe %s beitreten. Klicken Sie auf den folgenden Link, um direkt zur Studiengruppe zu gelangen.\n\n [Direkt zur Studiengruppe]%s"),
                 get_fullname($user_id),
                 $sem->getName(),
                 URLHelper::getlink(
diff --git a/lib/classes/TreeAbstract.class.php b/lib/classes/TreeAbstract.php
index ccdb6e1..a1413b3 100644
--- a/lib/classes/TreeAbstract.class.php
+++ b/lib/classes/TreeAbstract.php
@@ -5,7 +5,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// TreeAbstract.class.php
+// TreeAbstract.php
 // Abstract Base Class to handle in-memory tree structures
 //
 // Copyright (c) 2002 André Noack <noack@data-quest.de>
diff --git a/lib/classes/TreeView.class.php b/lib/classes/TreeView.php
index 243a9b9..0bc2810 100644
--- a/lib/classes/TreeView.class.php
+++ b/lib/classes/TreeView.php
@@ -5,8 +5,8 @@
 
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// TreeView.class.php
-// Class to print out html represantation of a tree object based on TreeAbstract.class.php
+// TreeView.php
+// Class to print out html represantation of a tree object based on TreeAbstract.php
 //
 // Copyright (c) 2002 André Noack <noack@data-quest.de>
 // Suchi & Berg GmbH <info@data-quest.de>
@@ -26,9 +26,7 @@
 // +---------------------------------------------------------------------------+
 
 /**
-* Class to print out html represantation of a tree object based on TreeAbstract.class.php
-*
-* Class to print out html represantation of a tree object based on TreeAbstract.class.php
+* Class to print out html represantation of a tree object based on TreeAbstract.php
 *
 * @access   public
 * @author   André Noack <noack@data-quest.de>
diff --git a/lib/classes/TwilloConnector.php b/lib/classes/TwilloConnector.php
index 7a57583..40ceff8 100644
--- a/lib/classes/TwilloConnector.php
+++ b/lib/classes/TwilloConnector.php
@@ -50,14 +50,14 @@ class TwilloConnector
     public static function uploadMaterial(OERMaterial $material, $user_id = null)
     {
         $user_id || $user_id = User::findCurrent()->id;
-        $base = new EduSharingHelperBase(
+        $base = new \EduSharingApiClient\EduSharingHelperBase(
             self::$twillo_base_url,
             file_get_contents($GLOBALS['STUDIP_BASE_PATH']."/config/twillo-private.key"),
             Config::get()->OERCAMPUS_TWILLO_APPID,
             self::getHttpProxy()
         // 'data-quest-Test'
         );
-        $authHelper = new EduSharingAuthHelper($base);
+        $authHelper = new \EduSharingApiClient\EduSharingAuthHelper($base);
         if (!static::$ticket) {
             static::$ticket = $authHelper->getTicketForUser(TwilloConnector::getTwilloUserID($user_id));
         }
@@ -261,13 +261,13 @@ class TwilloConnector
     {
         $user_id || $user_id = User::findCurrent()->id;
 
-        $base = new EduSharingHelperBase(
+        $base = new \EduSharingApiClient\EduSharingHelperBase(
             self::$twillo_base_url,
             file_get_contents($GLOBALS['STUDIP_BASE_PATH']."/config/twillo-private.key"),
             Config::get()->OERCAMPUS_TWILLO_APPID,
             self::getHttpProxy()// 'data-quest-Test'
         );
-        $authHelper = new EduSharingAuthHelper($base);
+        $authHelper = new \EduSharingApiClient\EduSharingAuthHelper($base);
         if (!static::$ticket) {
             static::$ticket = $authHelper->getTicketForUser(TwilloConnector::getTwilloUserID($user_id));
         }
diff --git a/lib/classes/UpdateInformation.class.php b/lib/classes/UpdateInformation.php
index 959ef72..959ef72 100644
--- a/lib/classes/UpdateInformation.class.php
+++ b/lib/classes/UpdateInformation.php
diff --git a/lib/classes/UserConfig.class.php b/lib/classes/UserConfig.php
index 4cb1ff6..413d4c8 100644
--- a/lib/classes/UserConfig.class.php
+++ b/lib/classes/UserConfig.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * UserConfig.class.php
+ * UserConfig.php
  * provides access to user preferences
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/UserDataAdapter.php b/lib/classes/UserDataAdapter.php
index 0a0c3be..5277145 100644
--- a/lib/classes/UserDataAdapter.php
+++ b/lib/classes/UserDataAdapter.php
@@ -26,66 +26,48 @@ class UserDataAdapter implements ArrayAccess, Countable, IteratorAggregate
 
     /**
      * ArrayAccess: Check whether the given offset exists.
-     *
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return $this->user->offsetExists($this->adaptOffset($offset));
     }
 
     /**
      * ArrayAccess: Get the value at the given offset.
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         return $this->user->offsetGet($this->adaptOffset($offset));
     }
 
     /**
      * ArrayAccess: Set the value at the given offset.
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
         $this->user->offsetSet($this->adaptOffset($offset), $value);
     }
 
     /**
      * ArrayAccess: unset the value at the given offset.
-     *
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
         $this->user->offsetUnset($this->adaptOffset($offset));
     }
 
     /**
      * @see Countable::count()
-     *
-     * @todo Add int return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function count()
+    public function count(): int
     {
         return $this->user->count();
     }
 
     /**
      * @see IteratorAggregate::getIterator()
-     *
-     * @todo Add Traversable return type when Stud.IP requires PHP8 minimal
      */
-    #[ReturnTypeWillChange]
-    public function getIterator()
+    public function getIterator(): Traversable
     {
         return $this->user->getIterator();
     }
diff --git a/lib/classes/UserLookup.class.php b/lib/classes/UserLookup.php
index ddf9276..62de8fd 100644
--- a/lib/classes/UserLookup.class.php
+++ b/lib/classes/UserLookup.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * UserLookup.class.php
+ * UserLookup.php
  *
  * provides an easy way to look up user ids by certain filter criteria
  *
@@ -239,7 +239,7 @@ class UserLookup
             return call_user_func(self::$types[$type]['values']);
         }
 
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         $cache_key = "UserLookup/{$type}/values";
         $cached_values = $cache->read($cache_key);
         if ($cached_values) {
diff --git a/lib/classes/UserManagement.class.php b/lib/classes/UserManagement.php
index c831b85..4bd47ec 100644
--- a/lib/classes/UserManagement.class.php
+++ b/lib/classes/UserManagement.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter007: TODO
 /**
- * UserManagement.class.php
+ * UserManagement.php
  *
  * Management for the Stud.IP global users
  *
@@ -25,7 +25,7 @@ require_once 'lib/messaging.inc.php';   // remove messages send or recieved by u
 require_once 'lib/object.inc.php';
 
 /**
- * UserManagement.class.php
+ * UserManagement.php
  *
  * Management for the Stud.IP global users
  *
@@ -898,7 +898,7 @@ class UserManagement
 
         // Load privacy plugins to ensure all event handlers can react to the
         // UserDataDidRemove event
-        PluginEngine::getPlugins('PrivacyPlugin');
+        PluginEngine::getPlugins(PrivacyPlugin::class);
 
         // delete user from instituts
         $this->logInstUserDel($this->user_data['auth_user_md5.user_id']);
@@ -1122,18 +1122,6 @@ class UserManagement
         // delete the datafields
         $localEntries = DataFieldEntry::removeAll($user_id);
 
-        // delete all blubber entrys
-        $query = "DELETE blubber_threads, blubber_mentions, blubber_comments
-                  FROM blubber_threads
-                  LEFT JOIN blubber_mentions USING (user_id)
-                  LEFT JOIN blubber_comments USING (user_id)
-                  WHERE user_id = ?";
-        $statement = DBManager::get()->prepare($query);
-        $statement->execute([$user_id]);
-        if ($count = $statement->rowCount()) {
-            $msg .= 'info§' . sprintf(_('%s Blubber gelöscht.'), $count) . '§';
-        }
-
         // delete user from waiting lists
         $query = "SELECT seminar_id FROM admission_seminar_user WHERE user_id = ?";
         $statement = DBManager::get()->prepare($query);
@@ -1221,8 +1209,6 @@ class UserManagement
             "DELETE FROM priorities WHERE user_id = ?",
             "DELETE FROM api_oauth_user_mapping WHERE user_id = ?",
             "DELETE FROM api_user_permissions WHERE user_id = ?",
-            "DELETE FROM eval_user WHERE user_id = ?",
-            "DELETE FROM evalanswer_user WHERE user_id = ?",
             "DELETE FROM help_tour_user WHERE user_id = ?",
             "DELETE FROM personal_notifications_user WHERE user_id = ?",
             "DELETE FROM forum_abo_users WHERE user_id = ?",
diff --git a/lib/classes/Visibility.php b/lib/classes/Visibility.php
index 1b87230..99b3907 100644
--- a/lib/classes/Visibility.php
+++ b/lib/classes/Visibility.php
@@ -614,7 +614,7 @@ class Visibility
     private function createHomepagePluginEntries($user)
     {
         self::getUser($user);
-        $homepageplugins = PluginEngine::getPlugins('HomepagePlugin');
+        $homepageplugins = PluginEngine::getPlugins(HomepagePlugin::class);
         foreach ($homepageplugins as $plugin) {
             self::addPrivacySetting($plugin->getPluginName(), ("plugin".$plugin->getPluginId()), 'plugins', 1, $user, null, $plugin->getPluginId());
         }
diff --git a/lib/classes/WidgetHelper.php b/lib/classes/WidgetHelper.php
deleted file mode 100644
index ba82ee9..0000000
--- a/lib/classes/WidgetHelper.php
+++ /dev/null
@@ -1,402 +0,0 @@
-<?php
-/**
- * WidgetHelper.php - utility functions for Widget-Parameter Handling
- * @deprecated since Stud.IP 5.5
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of
- * the License, or (at your option) any later version.
- *
- * @author   Nadine Werner <nadine.werner@uni-osnabrueck.de>
- * @author   André Klaßen <klassen@elan-ev.de>
- * @license  http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
- * @category Stud.IP
- * @package  index
- * @since    3.1
- */
-
-class WidgetHelper
-{
-    /**
-     * array of submitted widget parameter values
-     */
-    private static $params = [];
-
-    /**
-     * array of submitted widget parameter values
-     */
-    private static $activeWidget;
-
-    /**
-     * Saves the widget data of a user
-     */
-    private static $userWidgets = [];
-
-    /**
-     * Set the last active Widget
-     * @param string $activeWidget
-     */
-    public static function setActiveWidget($activeWidget)
-    {
-        self::$activeWidget = $activeWidget;
-    }
-
-    /**
-     * Returns the position in the two column layout on the Startpage
-     * If no position is stored in UserConfig, the widget will be displayed on the right side.
-     *
-     * @param string $pluginid
-     *
-     * @return the position as array matrix
-     */
-    public static function getWidgetPosition($pluginid)
-    {
-        $query = "SELECT position FROM widget_user where id = ?";
-        $statement = DBManager::get()->prepare($query);
-        $statement->execute([$pluginid]);
-        $pos = $statement->fetchColumn();
-
-        return $pos;
-    }
-
-    /**
-     * storeNewPositions - stores new Widget positions for a given user
-     *
-     * @param array $lanes array with column as index and ids array as value
-     *
-     * @return void
-     */
-    public static function storeNewPositions(array $lanes): void
-    {
-        // Query not displayed widgets to sort them to the bottom of a lane
-        $query = "SELECT `col`, `id`
-                  FROM `widget_user`
-                  WHERE `range_id` = ?
-                    AND `id` NOT IN (?)
-                  ORDER BY `col`, `position`";
-        $undisplayed = DBManager::get()->fetchGrouped($query, [
-            User::findCurrent()->id,
-            array_merge(...$lanes)
-        ], function ($row) {
-            return array_column($row, 'id');
-        });
-
-        // Set new positions
-        $query = "UPDATE `widget_user`
-                  SET `col` = :column,
-                      `position` = :position
-                  WHERE `id` = :id
-                    AND `range_id` = :user_id";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':user_id', User::findCurrent()->id);
-
-        foreach ([0, 1] as $column) {
-            $statement->bindValue(':column', $column);
-
-            $ids = array_merge(
-                $lanes[$column] ?? [],
-                $undisplayed[$column] ?? []
-            );
-
-            $position = 0;
-            foreach ($ids as $id) {
-                $statement->bindValue(':position', $position++);
-                $statement->bindValue(':id', $id);
-                $statement->execute();
-            }
-        }
-    }
-
-    /**
-     * addInitialPositons - adds the global widget default settings to an user setting
-     *
-     * @param string $col
-     * @param array $ids of widgets
-     * @param string $range_id
-     *
-     * @return void
-     */
-    public static function addInitialPositions($col, $ids, $range_id)
-    {
-        if(is_array($ids)) {
-             foreach ($ids as $pos => $id) {
-                  $pos = intVal($pos);
-                  $query = "REPLACE INTO widget_user (`pluginid`, `position`, `range_id`) VALUES (?,?,?);";
-                  $statement = DBManager::get()->prepare($query);
-                  $statement->execute([$id, $pos, $range_id]);
-             }
-        }
-    }
-
-    /**
-     * storeInitialPositions - stores the global widget default for a given perm
-     *
-     * @param string $col
-     * @param array $ids of widgets
-     * @param string $perm
-     *
-     * @return boolean success
-     */
-    public static function storeInitialPositions($col, $ids, $perm)
-    {
-        $stmt = DBManager::get()->prepare('DELETE FROM widget_default WHERE `perm` = ? AND `col` = ?;');
-        $stmt->execute([$perm, $col]);
-
-        if (is_array($ids)) {
-            foreach ($ids as $id => $pos) {
-                if ($id) {
-                    $pos = intVal($pos);
-                    $stmt = DBManager::get()->prepare("REPLACE INTO widget_default (`pluginid`,`col`, `position`, `perm`) VALUES (?,?,?,?);");
-                    $stmt->execute([$id, $col, $pos, $perm]);
-                }
-            }
-
-            return true;
-        }
-
-        return false;
-    }
-
-    public static function getInitialPositions($perm)
-    {
-        return DBManager::get()->fetchGroupedPairs("SELECT col, pluginid, position FROM widget_default "
-                . "WHERE perm = ? "
-                . "ORDER BY col ASC, position ASC", [$perm]);
-    }
-
-    /**
-     * Sets the current setting of a user as the default for a usergroup
-     *
-     * @param string $range_id The range id of the user that defines the setting
-     * @param string $group The usergroup
-     */
-    public static function setAsInitialPositions($range_id, $group)
-    {
-        DBManager::get()->execute("DELETE FROM widget_default WHERE `perm` = ?", [$group]);
-        DBManager::get()->execute('INSERT INTO widget_default (SELECT pluginid, col, position, ? as perm  FROM widget_user WHERE range_id = ?)', [$group, $range_id]);
-    }
-
-    /**
-     * setInitialPositions - copies the default to the logged on user
-     */
-    public static function setInitialPositions()
-    {
-        $query = "INSERT INTO widget_user (pluginid, position, range_id, col)
-                  SELECT pluginid, position, :user_id, col
-                  AS perm
-                  FROM widget_default
-                  WHERE perm = :perm
-
-                  UNION
-
-                  -- Dummy entry to allow no widgets
-                  SELECT -1, 0, :user_id, 2";
-        DBManager::get()->execute($query, [
-            ':user_id' => $GLOBALS['user']->id,
-            ':perm'    => $GLOBALS['perm']->get_perm(),
-        ]);
-    }
-
-    /**
-     * getUserWidgets - retrieves the widget settings for a given user
-     *
-     * @param string $id
-     *
-     * @return array $widgets
-     */
-    public static function getUserWidgets($id, $col = 0)
-    {
-        $plugin_manager = PluginManager::getInstance();
-        $query = "SELECT * FROM widget_user WHERE range_id=? AND col = ? ORDER BY position";
-        $statement = DBManager::get()->prepare($query);
-        $statement->execute([$id, $col]);
-        $widgets = [];
-        while ($db_widget = $statement->fetch(PDO::FETCH_ASSOC)) {
-            if(!is_null($plugin_manager->getPluginById($db_widget['pluginid']))){
-                $widget = clone $plugin_manager->getPluginById($db_widget['pluginid']);
-                $widget->widget_id = $db_widget['id'];
-                $widgets[$db_widget['position']] = $widget;
-            }
-        }
-        return $widgets;
-    }
-
-    /**
-     * Returns whether a user has any defined widgets.
-     * @param  string  $user_id User id
-     * @return boolean
-     */
-    public static function hasUserWidgets($user_id)
-    {
-        $query = "SELECT 1 FROM `widget_user` WHERE `range_id` = ?";
-        return (bool) DBManager::get()->fetchColumn($query, [$user_id]);
-    }
-
-    /**
-     * addWidgetUserConfig - creates user_config entry for widget newly added by a user
-     *
-     * @param string $id - user_id
-     * @param string $pluginName
-     * @param array $confArray
-     *
-     * @return void
-     */
-    public static function addWidgetUserConfig($id, $pluginName, $confArray )
-    {
-        UserConfig::get($id)->store($pluginName, $confArray );
-    }
-
-
-    /**
-     * getWidgetUserConfig - retrieves user_config entry for widget newly added by a user
-     *
-     * @param string $id user_id
-     * @param string $pluginName
-     *
-     * @return object UserConfig
-     */
-    public static function getWidgetUserConfig($id, $pluginName)
-    {
-        return UserConfig::get($id)->getValue($pluginName);
-
-    }
-
-    /**
-     * removeWidget - removes a widget for a user
-     *
-     * @param string $id - widget_id
-     * @param string $pluginName
-     * @param string $range_id e.g. user_id
-     *
-     * @return bool success
-     */
-    public static function removeWidget($id, $pluginName, $range_id)
-    {
-        UserConfig::get($range_id)->delete($pluginName);
-
-        $query = "DELETE FROM widget_user WHERE id = ? AND range_id = ?";
-        $statement = DBManager::get()->prepare($query);
-
-        return $statement->execute([$id, $range_id]);
-    }
-
-    /**
-     * addWidget - adds a widget for a given user
-     *
-     * @param string $id - widget_id
-     * @param string $range_id e.g. user_id
-     *
-     * @return bool|int false on error, id of inserted widget otherwise
-     */
-    public static function addWidget($id, $range_id)
-    {
-        $db = DBManager::get();
-        $statement = $db->prepare('SELECT MAX(position) + 1 FROM widget_user WHERE range_id = :range_id');
-        $statement->bindValue(':range_id', $range_id);
-        $statement->execute();
-        $position = $statement->fetchColumn() ?: 0;
-
-        $statement = $db->prepare('INSERT INTO widget_user (pluginid, position, range_id) VALUES (:id, :position, :range_id)');
-        $statement->bindValue(':id', $id);
-        $statement->bindValue(':position', $position);
-        $statement->bindValue(':range_id', $range_id);
-        $result = $statement->execute();
-
-        return $result ? $db->lastInsertId() : false;
-    }
-
-    /**
-     * getWidgetName - retrieves the name of a given widget
-     *
-     * @param string $id - widget_id
-     *
-     * @return string widget_name
-     */
-    public static function getWidgetName($id)
-    {
-        $query = "SELECT `pluginid` FROM `widget_user` WHERE `id`=?";
-        $statement = DBManager::get()->prepare($query);
-        $statement->execute([$id]);
-        $pid = $statement->fetch(PDO::FETCH_ASSOC);
-
-        $plugin_manager = PluginManager::getInstance();
-        $plugin_info = $plugin_manager->getPluginById($pid['pluginid']);
-        return $plugin_info ? $plugin_info->getPluginName() : false;
-
-    }
-
-
-    /**
-     * getWidget - retrieves an instance of a given widget / portal plugin
-     *
-     * @param string $pluginid
-     *
-     * @return object widget
-     */
-    public static function getWidget($pluginid)
-    {
-        return PluginManager::getInstance()->getPluginById($pluginid);
-    }
-
-    /**
-     * getAvailableWidgets - fetches all widgets that are not already in use.
-     *
-     * @param string $user_id the user to check
-     *
-     * @return array All available widgets.
-     */
-    public static function getAvailableWidgets($user_id = null)
-    {
-        $all_widgets = PluginEngine::getPlugins('PortalPlugin');
-
-        $used_widgets = is_null($user_id)
-                ? []
-                : DBManager::get()->fetchFirst("SELECT `pluginid` FROM `widget_user` WHERE `range_id`=? ORDER BY `pluginid`", [$user_id]);
-
-        $available = [];
-        foreach ($all_widgets as $widget) {
-            if (!in_array($widget->getPluginId(), $used_widgets)) {
-                $available[$widget->getPluginId()] = $widget;
-            }
-        }
-        return $available;
-    }
-
-    /**
-     * hasWidget - returns whether has a certain widget activated
-     *
-     * @param string $user_id Id of the user
-     * @param mixed  $widget  Id or name of the widget (you may omit the
-     *                        'Widget' in the name)
-     * @return bool indicating whether the widget is activated
-     */
-    public static function hasWidget($user_id, $widget)
-    {
-        if (!isset(self::$userWidgets[$user_id])) {
-            $statement = DBManager::get()->prepare("
-                SELECT *
-                FROM widget_user
-                WHERE range_id = :user_id
-            ");
-            $statement->execute(['user_id' => $user_id]);
-            self::$userWidgets[$user_id] = $statement->fetchAll(PDO::FETCH_ASSOC);
-        }
-
-        if (!ctype_digit($widget)) {
-            $plugin = PluginManager::getInstance()->getPlugin($widget) ?: PluginManager::getInstance()->getPlugin($widget . "Widget");
-            if ($plugin) {
-                $widget = $plugin->getPluginId();
-            } else {
-                return false;
-            }
-        }
-
-        foreach (self::$userWidgets[$user_id] as $widget_user) {
-            if ($widget_user['pluginid'] == $widget) {
-                return true;
-            }
-        }
-        return false;
-    }
-}
diff --git a/lib/classes/admission/AdmissionAlgorithm.class.php b/lib/classes/admission/AdmissionAlgorithm.php
index 7e9df92..fae1061 100644
--- a/lib/classes/admission/AdmissionAlgorithm.class.php
+++ b/lib/classes/admission/AdmissionAlgorithm.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * AdmissionAlgorithm.class.php
+ * AdmissionAlgorithm.php
  * 
  * Abstract class for seminar seat distribution. A concrete algorithm 
  * needs to be implemented.
@@ -32,4 +32,4 @@ abstract class AdmissionAlgorithm
 
 } /* end of class AdmissionAlgorithm */
 
-?>
\ No newline at end of file
+?>
diff --git a/lib/classes/admission/AdmissionPriority.class.php b/lib/classes/admission/AdmissionPriority.php
index 47e1564..22d426e 100644
--- a/lib/classes/admission/AdmissionPriority.class.php
+++ b/lib/classes/admission/AdmissionPriority.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * AdmissionPriority.class.php
+ * AdmissionPriority.php
  *
  * This class represents priorities a user has given to a set of courses.
  * No instance is needed, all methods are designed to be called statically.
diff --git a/lib/classes/admission/AdmissionRule.class.php b/lib/classes/admission/AdmissionRule.php
index fe5e5bb..2b826e4 100644
--- a/lib/classes/admission/AdmissionRule.class.php
+++ b/lib/classes/admission/AdmissionRule.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * AdmissionRule.class.php
+ * AdmissionRule.php
  *
  * An abstract representation of rules for course admission.
  *
diff --git a/lib/classes/admission/AdmissionUserList.class.php b/lib/classes/admission/AdmissionUserList.php
index 570bc62..3e5a430 100644
--- a/lib/classes/admission/AdmissionUserList.class.php
+++ b/lib/classes/admission/AdmissionUserList.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * AdmissionUserList.class.php
+ * AdmissionUserList.php
  *
  * Contains users that get different probabilities than others in seat
  * distribution algorithm.
diff --git a/lib/classes/admission/CourseSet.class.php b/lib/classes/admission/CourseSet.php
index d94bc05..cf87667 100644
--- a/lib/classes/admission/CourseSet.class.php
+++ b/lib/classes/admission/CourseSet.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * CourseSet.class.php
+ * CourseSet.php
  *
  * Represents groups of Stud.IP courses that have common rules for admission.
  *
diff --git a/lib/classes/admission/RandomAlgorithm.class.php b/lib/classes/admission/RandomAlgorithm.php
index 54d44d7..4666f59 100644
--- a/lib/classes/admission/RandomAlgorithm.class.php
+++ b/lib/classes/admission/RandomAlgorithm.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * RandomAlgorithm.class.php - Standard seat distribution algorithm
+ * RandomAlgorithm.php - Standard seat distribution algorithm
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
diff --git a/lib/classes/admission/UserFilter.class.php b/lib/classes/admission/UserFilter.php
index d380ef0..692422f 100644
--- a/lib/classes/admission/UserFilter.class.php
+++ b/lib/classes/admission/UserFilter.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * UserFilter.class.php
+ * UserFilter.php
  *
  * Conditions for user selection in Stud.IP. A condition is a collection of
  * condition fields, e.g. degree, course of study or semester. Each
diff --git a/lib/classes/admission/UserFilterField.class.php b/lib/classes/admission/UserFilterField.php
index 9081e90..4b51322 100644
--- a/lib/classes/admission/UserFilterField.class.php
+++ b/lib/classes/admission/UserFilterField.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * UserFilterField.class.php
+ * UserFilterField.php
  *
  * A specification of a Stud.IP condition that must be fulfilled. One
  * or more instances of the UserFilterField subclasses make up a
@@ -197,11 +197,10 @@ class UserFilterField
         if (self::$available_filter_fields === null) {
         $fields = [];
         // Load all PHP class files found in the condition field folder.
-        foreach (glob(realpath(dirname(__FILE__).'/userfilter').'/*.class.php') as $file) {
+        foreach (glob(realpath(dirname(__FILE__).'/userfilter').'/*.php') as $file) {
             require_once($file);
             // Try to auto-calculate class name from file name.
-            $className = mb_substr(basename($file), 0,
-                mb_strpos(basename($file), '.class.php'));
+            $className = mb_substr(basename($file), 0, mb_strpos(basename($file), '.php'));
             // Check if class is right.
             if (is_subclass_of($className, 'UserFilterField')) {
                 if ($className::$isParameterized) {
diff --git a/lib/classes/admission/userfilter/DatafieldCondition.class.php b/lib/classes/admission/userfilter/DatafieldCondition.php
index 966fe8e..1bc93e8 100644
--- a/lib/classes/admission/userfilter/DatafieldCondition.class.php
+++ b/lib/classes/admission/userfilter/DatafieldCondition.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * DatafieldCondition.class.php
+ * DatafieldCondition.php
  *
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/admission/userfilter/DegreeCondition.class.php b/lib/classes/admission/userfilter/DegreeCondition.php
index 9180e2d..61ce456 100644
--- a/lib/classes/admission/userfilter/DegreeCondition.class.php
+++ b/lib/classes/admission/userfilter/DegreeCondition.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * DegreeCondition.class.php
+ * DegreeCondition.php
  *
  * All conditions concerning the study degree in Stud.IP can be specified here.
  *
diff --git a/lib/classes/admission/userfilter/PermissionCondition.class.php b/lib/classes/admission/userfilter/PermissionCondition.php
index 4adfdbf..fe9458c 100644
--- a/lib/classes/admission/userfilter/PermissionCondition.class.php
+++ b/lib/classes/admission/userfilter/PermissionCondition.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * PermissionCondition.class.php
+ * PermissionCondition.php
  *
  * All conditions concerning the semester of study in Stud.IP can be specified here.
  *
diff --git a/lib/classes/admission/userfilter/SemesterOfStudyCondition.class.php b/lib/classes/admission/userfilter/SemesterOfStudyCondition.php
index 2c1233a..5794f75 100644
--- a/lib/classes/admission/userfilter/SemesterOfStudyCondition.class.php
+++ b/lib/classes/admission/userfilter/SemesterOfStudyCondition.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * SemesterOfStudyCondition.class.php
+ * SemesterOfStudyCondition.php
  *
  * All conditions concerning the semester of study in Stud.IP can be specified here.
  *
diff --git a/lib/classes/admission/userfilter/StgteilVersionCondition.class.php b/lib/classes/admission/userfilter/StgteilVersionCondition.php
index f6348e5..ec5c1f3 100644
--- a/lib/classes/admission/userfilter/StgteilVersionCondition.class.php
+++ b/lib/classes/admission/userfilter/StgteilVersionCondition.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * StgteilVersionCondition.class.php
+ * StgteilVersionCondition.php
  *
  * All conditions concerning the Studiengangteil-Versionen in Stud.IP can be specified here.
  *
diff --git a/lib/classes/admission/userfilter/SubjectCondition.class.php b/lib/classes/admission/userfilter/SubjectCondition.php
index ab44d49..7aa5f26 100644
--- a/lib/classes/admission/userfilter/SubjectCondition.class.php
+++ b/lib/classes/admission/userfilter/SubjectCondition.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * SubjectCondition.class.php
+ * SubjectCondition.php
  *
  * All conditions concerning the study subject in Stud.IP can be specified here.
  *
diff --git a/lib/classes/admission/userfilter/SubjectConditionAny.class.php b/lib/classes/admission/userfilter/SubjectConditionAny.php
index 107c86c..3a3712b 100644
--- a/lib/classes/admission/userfilter/SubjectConditionAny.class.php
+++ b/lib/classes/admission/userfilter/SubjectConditionAny.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * SubjectConditionAny.class.php
+ * SubjectConditionAny.php
  *
  * All conditions concerning the study subject in Stud.IP can be specified here.
  *
@@ -14,7 +14,7 @@
  * @category    Stud.IP
  */
 
-require_once realpath(__DIR__ . '/..') . '/UserFilterField.class.php';
+require_once realpath(__DIR__ . '/..') . '/UserFilterField.php';
 
 class SubjectConditionAny extends UserFilterField
 {
diff --git a/lib/classes/assets/SASSCompiler.php b/lib/classes/assets/SASSCompiler.php
index 2dcda2d..0b03a8c 100644
--- a/lib/classes/assets/SASSCompiler.php
+++ b/lib/classes/assets/SASSCompiler.php
@@ -2,7 +2,7 @@
 namespace Assets;
 
 use Assets;
-use StudipCacheFactory;
+use Studip\Cache\Factory;
 use Studip;
 
 use ScssPhp\ScssPhp\Compiler as ScssCompiler;
@@ -82,7 +82,7 @@ class SASSCompiler implements Compiler
      */
     private function getPrefix()
     {
-        $cache = StudipCacheFactory::getCache();
+        $cache = Studip\Cache\Factory::getCache();
 
         $prefix = $cache->read(self::CACHE_KEY);
 
diff --git a/lib/classes/auth_plugins/StudipAuthAbstract.class.php b/lib/classes/auth_plugins/StudipAuthAbstract.php
index 36c75df..19d5afa 100644
--- a/lib/classes/auth_plugins/StudipAuthAbstract.class.php
+++ b/lib/classes/auth_plugins/StudipAuthAbstract.php
@@ -1,7 +1,7 @@
 <?php
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipAuthAbstract.class.php
+// StudipAuthAbstract.php
 // Abstract class, used as a template for authentication plugins
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/auth_plugins/StudipAuthCAS.class.php b/lib/classes/auth_plugins/StudipAuthCAS.php
index 29deb75..29deb75 100644
--- a/lib/classes/auth_plugins/StudipAuthCAS.class.php
+++ b/lib/classes/auth_plugins/StudipAuthCAS.php
diff --git a/lib/classes/auth_plugins/StudipAuthIP.class.php b/lib/classes/auth_plugins/StudipAuthIP.php
index e0d6afa..dd42a28 100644
--- a/lib/classes/auth_plugins/StudipAuthIP.class.php
+++ b/lib/classes/auth_plugins/StudipAuthIP.php
@@ -1,6 +1,6 @@
 <?php
 /*
- * StudipAuthIP.class.php - Stud.IP authentication with user ip
+ * StudipAuthIP.php - Stud.IP authentication with user ip
  * Copyright (c) 2014  Florian Bieringer, Uni Passau
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/auth_plugins/StudipAuthLTI.class.php b/lib/classes/auth_plugins/StudipAuthLTI.php
index e8c316f..d5a2863 100644
--- a/lib/classes/auth_plugins/StudipAuthLTI.class.php
+++ b/lib/classes/auth_plugins/StudipAuthLTI.php
@@ -1,6 +1,6 @@
 <?php
 /*
- * StudipAuthLTI.class.php - Stud.IP authentication against LTI 1.1 consumer
+ * StudipAuthLTI.php - Stud.IP authentication against LTI 1.1 consumer
  * Copyright (c) 2018  Elmar Ludwig
  *
  * This program is free software; you can redistribute it and/or
@@ -9,8 +9,12 @@
  * the License, or (at your option) any later version.
  */
 
+use Studip\OAuth2\NegotiatesWithPsr7;
+
 class StudipAuthLTI extends StudipAuthSSO
 {
+    use NegotiatesWithPsr7;
+
     public $consumer_keys;
     public $username;
     public $domain;
@@ -62,24 +66,15 @@ class StudipAuthLTI extends StudipAuthSSO
      *
      * @return  bool    true if authentication succeeds
      *
-     * @throws OAuthException2  if the signature verification failed
-     *
      */
     public function isAuthenticated($username, $password)
     {
-        require_once 'vendor/oauth-php/library/OAuthRequestVerifier.php';
-
-        OAuthStore::instance('PDO', [
-            'dsn' => 'mysql:host=' . $GLOBALS['DB_STUDIP_HOST'] . ';dbname=' . $GLOBALS['DB_STUDIP_DATABASE'],
-            'username' => $GLOBALS['DB_STUDIP_USER'],
-            'password' => $GLOBALS['DB_STUDIP_PASSWORD']
-        ]);
-
         $consumer_key = Request::get('oauth_consumer_key');
         $consumer_secret = $this->consumer_keys[$consumer_key]['consumer_secret'];
 
-        $oarv = new OAuthRequestVerifier();
-        $oarv->verifySignature($consumer_secret, false, false);
+        if (!Studip\OAuth1::verifyRequest($this->getPsrRequest(), $consumer_secret, '')) {
+            return false;
+        }
 
         return parent::isAuthenticated($username, $password);
     }
@@ -93,8 +88,6 @@ class StudipAuthLTI extends StudipAuthSSO
      * @param   string $password the password (ignored)
      *
      * @return  mixed   if authentication succeeds: the Stud.IP user, else false
-     *
-     * @throws OAuthException2  if the signature verification failed
      */
     public function authenticateUser($username, $password)
     {
diff --git a/lib/classes/auth_plugins/StudipAuthLdap.class.php b/lib/classes/auth_plugins/StudipAuthLdap.php
index 7cb8686..6bbd3fd 100644
--- a/lib/classes/auth_plugins/StudipAuthLdap.class.php
+++ b/lib/classes/auth_plugins/StudipAuthLdap.php
@@ -1,7 +1,7 @@
 <?php
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipAuthLdap.class.php
+// StudipAuthLdap.php
 // Stud.IP authentication against LDAP Server
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/auth_plugins/StudipAuthLdapReadAndBind.class.php b/lib/classes/auth_plugins/StudipAuthLdapReadAndBind.php
index 742f0cb..3acb1d8 100644
--- a/lib/classes/auth_plugins/StudipAuthLdapReadAndBind.class.php
+++ b/lib/classes/auth_plugins/StudipAuthLdapReadAndBind.php
@@ -4,7 +4,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipAuthLdapReadAndBind.class.php
+// StudipAuthLdapReadAndBind.php
 // Stud.IP authentication against LDAP Server using read-only account and
 // user bind
 //
diff --git a/lib/classes/auth_plugins/StudipAuthOIDC.class.php b/lib/classes/auth_plugins/StudipAuthOIDC.php
index adfe9c9..b26c17b 100644
--- a/lib/classes/auth_plugins/StudipAuthOIDC.class.php
+++ b/lib/classes/auth_plugins/StudipAuthOIDC.php
@@ -1,6 +1,6 @@
 <?php
 /*
- * StudipAuthOpenID.class.php - Stud.IP authentication using OpenID Connect
+ * StudipAuthOpenID.php - Stud.IP authentication using OpenID Connect
  * Copyright (c) 2021  André Noack <noack@data-quest.de>
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/auth_plugins/StudipAuthSSO.class.php b/lib/classes/auth_plugins/StudipAuthSSO.php
index 752fa59..dd6af11 100644
--- a/lib/classes/auth_plugins/StudipAuthSSO.class.php
+++ b/lib/classes/auth_plugins/StudipAuthSSO.php
@@ -3,7 +3,7 @@
 # Lifter003: TODO
 # Lifter010: TODO
 /*
- * StudipAuthSSO.class.php - abstract base class for SSO auth plugins
+ * StudipAuthSSO.php - abstract base class for SSO auth plugins
  * Copyright (c) 2007  Elmar Ludwig, Universitaet Osnabrueck
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/auth_plugins/StudipAuthShib.class.php b/lib/classes/auth_plugins/StudipAuthShib.php
index 3eedc65..135b3f6 100644
--- a/lib/classes/auth_plugins/StudipAuthShib.class.php
+++ b/lib/classes/auth_plugins/StudipAuthShib.php
@@ -3,7 +3,7 @@
 # Lifter003: TODO
 # Lifter010: TODO
 /*
- * StudipAuthShib.class.php - Stud.IP authentication against Shibboleth server
+ * StudipAuthShib.php - Stud.IP authentication against Shibboleth server
  * Copyright (c) 2007  Elmar Ludwig, Universitaet Osnabrueck
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/auth_plugins/StudipAuthStandard.class.php b/lib/classes/auth_plugins/StudipAuthStandard.php
index 5bb3e65..927a13c 100644
--- a/lib/classes/auth_plugins/StudipAuthStandard.class.php
+++ b/lib/classes/auth_plugins/StudipAuthStandard.php
@@ -4,7 +4,7 @@
 # Lifter010: TODO
 // +---------------------------------------------------------------------------+
 // This file is part of Stud.IP
-// StudipAuthStandard.class.php
+// StudipAuthStandard.php
 // Basic Stud.IP authentication, using the Stud.IP database
 //
 // Copyright (c) 2003 André Noack <noack@data-quest.de>
diff --git a/lib/classes/cache/Cache.php b/lib/classes/cache/Cache.php
new file mode 100644
index 0000000..be703cf
--- /dev/null
+++ b/lib/classes/cache/Cache.php
@@ -0,0 +1,213 @@
+<?php
+
+namespace Studip\Cache;
+
+use Psr\Cache\CacheItemInterface;
+use Psr\Cache\CacheItemPoolInterface;
+
+/**
+ * An abstract class which has to be extended by instances returned from
+ * \Studip\Cache\Factory#getCache
+ *
+ * @author     Marco Diedrich (mdiedric@uos)
+ * @author     Marcus Lunzenauer (mlunzena@uos.de)
+ * @author     Moritz Strohm <strohm@data-quest.de>
+ * @copyright  (c) Authors
+ * @since      1.6
+ * @license    GPL2 or any later version
+ */
+abstract class Cache implements CacheItemPoolInterface
+{
+    const DEFAULT_EXPIRATION = 12 * 60 * 60; // 12 hours
+
+    /**
+     * @return string A translateable display name for this cache class.
+     */
+    abstract public static function getDisplayName(): string;
+
+    /**
+     * Get some statistics from cache, like number of entries, hit rate or
+     * whatever the underlying cache provides.
+     * Results are returned in form of an array like
+     *      "[
+     *          [
+     *              'name' => <displayable name>
+     *              'value' => <value of the current stat>
+     *          ]
+     *      ]"
+     *
+     * @return array
+     */
+    abstract public function getStats(): array;
+
+    /**
+     * Return the Vue component name and props that handle configuration.
+     * The associative array is of the form
+     *  [
+     *      'component' => <Vue component name>,
+     *      'props' => <Properties for component>
+     *  ]
+     *
+     * @return array
+     */
+    abstract public static function getConfig(): array;
+
+    /**
+     * Expire item from the cache.
+     *
+     * Example:
+     *
+     *   # expires foo
+     *   $cache->expire('foo');
+     *
+     * @param string $arg a single key
+     */
+    abstract public function expire($arg);
+
+    /**
+     * Expire all items from the cache.
+     */
+    abstract public function flush();
+
+    /**
+     * @see CacheItemPoolInterface::getItem
+     */
+    abstract public function getItem(string $key): CacheItemInterface;
+
+    /**
+     * @see CacheItemPoolInterface::hasItem
+     */
+    abstract public function hasItem(string $key): bool;
+
+    /**
+     * @var array An array of deferred items that shall be saved only
+     * when commit() is called. This is only used in PSR-6 cache methods.
+     */
+    protected array $deferred_items = [];
+
+    /**
+     * Retrieve item from the server.
+     *
+     * Example:
+     *
+     *   # reads foo
+     *   $foo = $cache->reads('foo');
+     *
+     * @param string $arg a single key
+     *
+     * @return mixed    the previously stored data if an item with such a key
+     *                  exists on the server or FALSE on failure.
+     *
+     * @deprecated To be removed with Stud.IP 7.0.
+     */
+    public function read($arg)
+    {
+        $item = $this->getItem($arg);
+        if ($item->isHit()) {
+            return $item->get();
+        }
+        return false;
+    }
+
+    /**
+     * Store data at the server.
+     *
+     * @param string $name     the item's key.
+     * @param mixed  $content  the item's content (will be serialized if necessary).
+     * @param int    $expires  the item's expiry time in seconds. Optional, defaults to 12h.
+     *
+     * @return bool     returns TRUE on success or FALSE on failure.
+
+     * @deprecated To be removed with Stud.IP 7.0.
+     */
+    public function write($name, $content, $expires = self::DEFAULT_EXPIRATION)
+    {
+        $item = new Item($name, $content, $expires);
+
+        return $this->save($item);
+    }
+
+    /**
+     * Calculates the expiration by a cache item. If that cannot be determined,
+     * the default expiration period is returned.
+     *
+     * @param Item $item The item from which to get the expiration time.
+     *
+     * @return int The time from now until the expiration in seconds.
+     */
+    public function getExpiration(CacheItemInterface $item) : int
+    {
+        $expiration = self::DEFAULT_EXPIRATION;
+        if ($item instanceof Item) {
+            $expiration = $item->getExpirationInSeconds();
+        }
+        return $expiration;
+    }
+
+    // PSR-6 CacheItemPoolInterface:
+
+    /**
+     * @see CacheItemPoolInterface::getItems
+     */
+    public function getItems(array $keys = []): iterable
+    {
+        $items = [];
+        foreach ($keys as $key) {
+            $item = $this->getItem($key);
+            if ($item instanceof Item) {
+                $items[] = $item;
+            }
+        }
+        return $items;
+    }
+
+    /**
+     * @see CacheItemPoolInterface::clear
+     */
+    public function clear(): bool
+    {
+        $this->deferred_items = [];
+        $this->flush();
+        return true;
+    }
+
+    /**
+     * @see CacheItemPoolInterface::deleteItem
+     */
+    public function deleteItem($key): bool
+    {
+        $this->expire($key);
+        return true;
+    }
+
+    /**
+     * @see CacheItemPoolInterface::deleteItems
+     */
+    public function deleteItems(array $keys): bool
+    {
+        foreach ($keys as $key) {
+            $this->expire($key);
+        }
+        return true;
+    }
+
+    /**
+     * @see CacheItemPoolInterface::saveDeferred
+     */
+    public function saveDeferred(CacheItemInterface $item): bool
+    {
+        $this->deferred_items[] = $item;
+        return true;
+    }
+
+    /**
+     * @see CacheItemPoolInterface::commit
+     */
+    public function commit(): bool
+    {
+        foreach ($this->deferred_items as $item) {
+            $this->save($item);
+        }
+        return true;
+    }
+}
diff --git a/lib/classes/cache/DbCache.php b/lib/classes/cache/DbCache.php
new file mode 100644
index 0000000..c7abef2
--- /dev/null
+++ b/lib/classes/cache/DbCache.php
@@ -0,0 +1,143 @@
+<?php
+
+namespace Studip\Cache;
+
+use DBManager;
+use Psr\Cache\CacheItemInterface;
+
+/**
+ * StudipCache implementation using database table
+ *
+ * @author    Elmar Ludwig <elmar.ludwig@uos.de>
+ */
+class DbCache extends Cache
+{
+    /**
+     * @return string A display name (that can be translated) for this cache class.
+     */
+    public static function getDisplayName(): string
+    {
+        return _('Datenbank');
+    }
+
+    /**
+     * Expire item from the cache.
+     *
+     * @param string $arg a single key
+     */
+    public function expire($arg)
+    {
+        $db = DBManager::get();
+
+        $stmt = $db->prepare('DELETE FROM cache WHERE cache_key = ?');
+        $stmt->execute([$arg]);
+    }
+
+    /**
+     * Expire all items from the cache.
+     */
+    public function flush()
+    {
+        $db = DBManager::get();
+
+        $db->exec('TRUNCATE TABLE cache');
+    }
+
+    /**
+     * Delete all expired items from the cache.
+     */
+    public function purge()
+    {
+        $db = DBManager::get();
+
+        $stmt = $db->prepare('DELETE FROM cache WHERE expires < ?');
+        $stmt->execute([time()]);
+    }
+
+    /**
+     * Return statistics.
+     *
+     * @return array|array[]
+     *@see Cache::getStats()
+     *
+     */
+    public function getStats(): array
+    {
+        return [
+            __CLASS__ => [
+                'name' => _('Anzahl Einträge'),
+                'value' => DBManager::get()->fetchColumn("SELECT COUNT(*) FROM `cache`")
+            ]
+        ];
+    }
+
+    /**
+     * Return the Vue component name and props that handle configuration.
+     *
+     * @return array
+     *@see Cache::getConfig()
+     *
+     */
+    public static function getConfig(): array
+    {
+        return [
+            'component' => null,
+            'props' => []
+        ];
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function getItem(string $key): CacheItemInterface
+    {
+        $query = "SELECT `content`, `expires`
+                  FROM `cache`
+                  WHERE `cache_key` = :key
+                    AND `expires` > UNIX_TIMESTAMP()";
+        $result = DBManager::get()->fetchOne($query, [':key' => $key]);
+
+        $item = new Item($key);
+        if (!empty($result)) {
+            $item->setHit();
+            if ($result['content']) {
+                $item->set(unserialize($result['content']));
+            }
+            if ($result['expires']) {
+                $expiration = new \DateTime();
+                $expiration->setTimestamp($result['expires']);
+                $item->expiresAt($expiration);
+            }
+        }
+        return $item;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function hasItem(string $key): bool
+    {
+        $query = "SELECT 1
+                  FROM `cache`
+                  WHERE `cache_key` = :key
+                    AND `expires` > UNIX_TIMESTAMP()";
+        return (bool) DBManager::get()->fetchColumn($query, [':key' => $key]);
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function save(CacheItemInterface $item): bool
+    {
+        $expiration = $this->getExpiration($item);
+        if ($expiration < 1) {
+            // The item would expire immediately.
+            return false;
+        }
+
+        return DBManager::get()->execute(
+            'REPLACE INTO `cache` VALUES (?, ?, ?)',
+            [$item->getKey(), serialize($item->get()), $expiration]
+        );
+    }
+}
diff --git a/lib/classes/cache/Exception.php b/lib/classes/cache/Exception.php
new file mode 100644
index 0000000..061d090
--- /dev/null
+++ b/lib/classes/cache/Exception.php
@@ -0,0 +1,27 @@
+<?php
+/*
+ * CacheException.php
+ * This file is part of Stud.IP.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Moritz Strohm <strohm@data-quest.de>
+ * @copyright   2024
+ * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
+ * @category    Stud.IP
+ * @since       6.0
+ */
+
+namespace Studip\Cache;
+
+/**
+ * The CacheException class is an implementation of the CacheException interface
+ * of PSR-6 that behaves like a StudipException.
+ */
+class Exception extends \StudipException implements \Psr\Cache\CacheException
+{
+    //Nothing here, since there is nothing to implement.
+}
diff --git a/lib/classes/StudipCacheFactory.class.php b/lib/classes/cache/Factory.php
index 77c5973..b5c8359 100644
--- a/lib/classes/StudipCacheFactory.class.php
+++ b/lib/classes/cache/Factory.php
@@ -1,4 +1,15 @@
 <?php
+
+namespace Studip\Cache;
+
+use Config;
+use DBSchemaVersion;
+use MessageBox;
+use PageLayout;
+use ReflectionClass;
+use StudipCacheOperation;
+use UnexpectedValueException;
+
 /**
  * This factory retrieves the instance of StudipCache configured for use in
  * this Stud.IP installation.
@@ -12,30 +23,29 @@
  * @since     1.6
  * @license   GPL2 or any later version
  */
-
-class StudipCacheFactory
+class Factory
 {
     /**
      * the default cache class
      *
      * @var string
      */
-    const DEFAULT_CACHE_CLASS = StudipDbCache::class;
+    const DEFAULT_CACHE_CLASS = DbCache::class;
 
     /**
      * singleton instance
      *
-     * @var StudipCache
+     * @var Cache|null
      */
-    private static $cache;
+    private static ?Cache $cache = null;
 
 
     /**
      * config instance
      *
-     * @var Config
+     * @var Config|null
      */
-    private static $config = null;
+    private static ?Config $config = null;
 
 
     /**
@@ -49,7 +59,7 @@ class StudipCacheFactory
      */
     public static function getConfig()
     {
-        return is_null(self::$config) ? Config::getInstance() : self::$config;
+        return self::$config ?? Config::getInstance();
     }
 
 
@@ -58,7 +68,7 @@ class StudipCacheFactory
      *                       determine the class of the implementation of interface
      *                       StudipCache
      */
-    public static function setConfig($config)
+    public static function setConfig(Config $config)
     {
         self::$config = $config;
         self::$cache = NULL;
@@ -77,15 +87,15 @@ class StudipCacheFactory
      *
      * @param bool $apply_proxied_operations Whether or not to apply any
      *                                       proxied (disable this in tests!)
-     * @return StudipCache the cache instance
+     * @return Cache the cache instance
      */
-    public static function getCache($apply_proxied_operations = true)
+    public static function getCache(bool $apply_proxied_operations = true): Cache
     {
-        if (is_null(self::$cache)) {
+        if (self::$cache === null) {
             $proxied = false;
 
             if (!$GLOBALS['CACHING_ENABLE']) {
-                self::$cache = new StudipMemoryCache();
+                self::$cache = new MemoryCache();
 
                 // Proxy cache operations if CACHING_ENABLE is different from the globally set
                 // caching value. This should only be the case in cli mode.
@@ -98,7 +108,7 @@ class StudipCacheFactory
                     $args = self::retrieveConstructorArguments();
 
                     self::$cache = self::instantiateCache($class, $args);
-                } catch (Exception $e) {
+                } catch (\Exception $e) {
                     error_log(__METHOD__ . ': ' . $e->getMessage());
                     PageLayout::addBodyElements(MessageBox::error(__METHOD__ . ': ' . $e->getMessage()));
                     $class = self::DEFAULT_CACHE_CLASS;
@@ -109,7 +119,7 @@ class StudipCacheFactory
             // If proxy should be used, inject it. Otherwise apply pending
             // operations, if any.
             if ($proxied) {
-                self::$cache = new StudipCacheProxy(self::$cache);
+                self::$cache = new Proxy(self::$cache);
             } elseif ($GLOBALS['CACHING_ENABLE'] && $apply_proxied_operations) {
                 // Even if the above condition will try to eliminate most
                 // failures, the following operation still needs to be wrapped
@@ -118,7 +128,7 @@ class StudipCacheFactory
                 // for said operation.
                 try {
                     StudipCacheOperation::apply(self::$cache);
-                } catch (Exception $e) {
+                } catch (\Exception $e) {
                 }
             }
         }
@@ -174,10 +184,11 @@ class StudipCacheFactory
      * memory cache is instantiated, the cache will be wrapped in a wrapper
      * class that uses a memory cache to reduce accesses to the cache.
      *
-     * @param  string $class     the name of the class
-     * @param  array  $arguments an array of arguments to be used by the constructor
+     * @param string $class     the name of the class
+     * @param array  $arguments an array of arguments to be used by the constructor
      *
-     * @return StudipCache  an instance of the specified class
+     * @return Cache  an instance of the specified class
+     * @throws \ReflectionException
      */
     public static function instantiateCache($class, $arguments)
     {
@@ -186,8 +197,8 @@ class StudipCacheFactory
                ? $reflection_class->newInstanceArgs($arguments['config'])
                : $reflection_class->newInstance();
 
-        if ($class !== StudipMemoryCache::class) {
-            return new StudipCacheWrapper($cache);
+        if ($class !== MemoryCache::class) {
+            return new Wrapper($cache);
         }
 
         return $cache;
diff --git a/lib/classes/StudipFileCache.class.php b/lib/classes/cache/FileCache.php
index 9eae66c..d760f08 100644
--- a/lib/classes/StudipFileCache.class.php
+++ b/lib/classes/cache/FileCache.php
@@ -1,46 +1,28 @@
 <?php
-# Lifter010: TODO
-// +--------------------------------------------------------------------------+
-// This file is part of Stud.IP
-// StudipFileCache.class.php
-//
-//
-//
-// Copyright (c) 2007 André Noack <noack@data-quest.de>
-// +--------------------------------------------------------------------------+
-// This program is free software; you can redistribute it and/or
-// modify it under the terms of the GNU General Public License
-// as published by the Free Software Foundation; either version 2
-// of the License, or any later version.
-// +--------------------------------------------------------------------------+
-// This program is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-// You should have received a copy of the GNU General Public License
-// along with this program; if not, write to the Free Software
-// Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
-// +--------------------------------------------------------------------------+
+
+namespace Studip\Cache;
+
+use Config;
+use Exception;
+use Psr\Cache\CacheItemInterface;
 
 /**
- * StudipCache implementation using files
- *
- * @package     studip
- * @subpackage  cache
+ * Cache implementation using files
  *
  * @author    André Noack <noack@data-quest.de>
- * @version   2
+ * @copyright 2007 André Noack <noack@data-quest.de>
+ * @license GPL2 or any later version
  */
-class StudipFileCache implements StudipCache
+class FileCache extends Cache
 {
-    use StudipCacheKeyTrait;
+    use KeyTrait;
 
     /**
      * full path to cache directory
      *
      * @var string
      */
-    private $dir;
+    private string $dir;
 
     /**
      * @return string A translateable display name for this cache class.
@@ -55,26 +37,28 @@ class StudipFileCache implements StudipCache
      * $CACHING_FILECACHE_PATH or is set to
      * $TMP_PATH/studip_cache
      *
-     * @param string the path to use
-     * @return void
-     * @throws exception if the directory does not exist or could not be
+     * @param string $path the path to use
+     * @throws Exception if the directory does not exist or could not be
      *         created
      */
-    public function __construct($path = '')
+    public function __construct(string $path = '')
     {
         $this->dir = $path
-                  ?: (Config::get()->SYSTEMCACHE['type'] == 'StudipFileCache' ?
-                        Config::get()->SYSTEMCACHE['config']['path'] : '')
+                  ?: (
+                      Config::get()->SYSTEMCACHE['type'] === self::class
+                          ? Config::get()->SYSTEMCACHE['config']['path']
+                          : ''
+                  )
                   ?: $GLOBALS['CACHING_FILECACHE_PATH']
                   ?: ($GLOBALS['TMP_PATH'] . '/' . 'studip_cache');
         $this->dir = rtrim($this->dir, '\\/') . '/';
 
         if (!is_dir($this->dir) && !@mkdir($this->dir, 0700)) {
-            throw new Exception('Could not create directory: ' . $this->dir);
+            throw new \Exception('Could not create directory: ' . $this->dir);
         }
 
         if (!is_writable($this->dir)) {
-            throw new Exception('Can not write to directory: ' . $this->dir);
+            throw new \Exception('Can not write to directory: ' . $this->dir);
         }
     }
 
@@ -91,9 +75,11 @@ class StudipFileCache implements StudipCache
     /**
      * expire cache item
      *
-     * @see StudipCache::expire()
      * @param string $arg
+     *
      * @return void
+     * @throws Exception
+     * @see Cache::expire()
      */
     public function expire($arg)
     {
@@ -113,61 +99,20 @@ class StudipFileCache implements StudipCache
     }
 
     /**
-     * retrieve cache item from filesystem
-     * tests first if item is expired
-     *
-     * @see StudipCache::read()
-     * @param string $arg a cache key
-     * @return string|bool
-     */
-    public function read($arg)
-    {
-        $key = $this->getCacheKey($arg);
-
-        if ($file = $this->check($key)){
-            $f = @fopen($file, 'rb');
-            if ($f) {
-                @flock($f, LOCK_SH);
-                $result = stream_get_contents($f);
-                @fclose($f);
-            }
-            return unserialize($result);
-        }
-        return false;
-    }
-
-    /**
-     * store data as cache item in filesystem
-     *
-     * @see StudipCache::write()
-     * @param string $arg a cache key
-     * @param mixed $content data to store
-     * @param int $expire expiry time in seconds, default 12h
-     * @return int|bool the number of bytes that were written to the file,
-     *         or false on failure
-     */
-    public function write($arg, $content, $expire = self::DEFAULT_EXPIRATION)
-    {
-        $key = $this->getCacheKey($arg);
-
-        $this->expire($key);
-        $file = $this->getPathAndFile($key, $expire);
-        return @file_put_contents($file, serialize($content), LOCK_EX);
-    }
-
-    /**
      * checks if specified cache item is expired
      * if expired the cache file is deleted
      *
      * @param string $key a cache key to check
-     * @return string|bool the path to the cache file or false if expired
+     *
+     * @return array|bool the path to the cache file or false if expired
+     * @throws Exception
      */
     private function check($key)
     {
         if ($file = $this->getPathAndFile($key)){
-            list($id, $expire) = explode('-', basename($file));
+            [$id, $expire] = explode('-', basename($file));
             if (time() < $expire) {
-                return $file;
+                return [$file, $expire];
             } else {
                 @unlink($file);
             }
@@ -183,16 +128,18 @@ class StudipFileCache implements StudipCache
      * the filename is constructed from the hashed cache key
      * and the timestamp of expiration
      *
-     * @param string $key a cache key
-     * @param int $expire expiry time in seconds
+     * @param string   $key    a cache key
+     * @param int|null $expire expiry time in seconds
+     *
      * @return string|bool full path to cache item or false on failure
+     * @throws Exception
      */
-    private function getPathAndFile($key, $expire = null)
+    private function getPathAndFile(string $key, ?int $expire = null): bool|string
     {
         $id = hash('md5', $key);
         $path = $this->dir . mb_substr($id, 0, 2);
         if (!is_dir($path) && !@mkdir($path, 0700)) {
-            throw new Exception('Could not create directory: ' . $path);
+            throw new \Exception('Could not create directory: ' . $path);
         }
         if (!is_null($expire)){
             return $path . '/' . $id . '-' . (time() + $expire);
@@ -208,16 +155,17 @@ class StudipFileCache implements StudipCache
     /**
      * purges expired entries from the cache directory
      *
-     * @param bool echo messages if set to false
+     * @param bool $be_quiet echo messages if set to false
+     *
      * @return int the number of deleted files
      */
-    public function purge($be_quiet = true)
+    public function purge(bool $be_quiet = true): int
     {
         $now = time();
         $deleted = 0;
         foreach (@glob($this->dir . '*', GLOB_ONLYDIR) as $current_dir){
             foreach (@glob("{$current_dir}/*") as $file){
-                list($id, $expire) = explode('-', basename($file));
+                [$id, $expire] = explode('-', basename($file));
                 if ($expire < $now) {
                     if (@unlink($file)) {
                         ++$deleted;
@@ -225,8 +173,8 @@ class StudipFileCache implements StudipCache
                             echo "File: {$file} deleted.\n";
                         }
                     }
-                } else if (!$be_quiet){
-                    echo "File: {$file} expires on " . strftime('%x %X', $expire) . "\n";
+                } else if (!$be_quiet) {
+                    echo "File: {$file} expires on " . date('Y-m-d H:i:s', $expire) . "\n";
                 }
             }
         }
@@ -243,7 +191,7 @@ class StudipFileCache implements StudipCache
         return [
             __CLASS__ => [
                 'name' => _('Anzahl Einträge'),
-                'value' => DBManager::get()->fetchColumn("SELECT COUNT(*) FROM `cache`")
+                'value' => \DBManager::get()->fetchColumn("SELECT COUNT(*) FROM `cache`")
             ]
         ];
     }
@@ -273,4 +221,58 @@ class StudipFileCache implements StudipCache
         ];
     }
 
+    /**
+     * @inheritDoc
+     */
+    public function getItem(string $key): CacheItemInterface
+    {
+        $real_key = $this->getCacheKey($key);
+
+        $item = new \Studip\Cache\Item($key);
+
+        $file_data = $this->check($real_key);
+        if ($file_data) {
+            $file = $file_data[0];
+            $expire = $file_data[1];
+            $f = @fopen($file, 'rb');
+            if ($f) {
+                @flock($f, LOCK_SH);
+                $result = stream_get_contents($f);
+                @fclose($f);
+            }
+            $item->setHit();
+            $item->set(unserialize($result));
+            $expiration = new \DateTime();
+            $expiration->setTimestamp($expire);
+            $item->expiresAt($expiration);
+        }
+        return $item;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function hasItem(string $key): bool
+    {
+        $real_key = $this->getCacheKey($key);
+        $file_data = $this->check($real_key);
+        return $file_data !== false;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function save(CacheItemInterface $item): bool
+    {
+        $expiration = $this->getExpiration($item);
+        if ($expiration < 1) {
+            //The item would expire immediately.
+            return false;
+        }
+
+        $real_key = $this->getCacheKey($item->getKey());
+        $this->expire($real_key);
+        $file = $this->getPathAndFile($real_key, $expiration);
+        return @file_put_contents($file, serialize($item->get()), LOCK_EX);
+    }
 }
diff --git a/lib/classes/cache/InvalidCacheArgumentException.php b/lib/classes/cache/InvalidCacheArgumentException.php
new file mode 100644
index 0000000..a201cad
--- /dev/null
+++ b/lib/classes/cache/InvalidCacheArgumentException.php
@@ -0,0 +1,28 @@
+<?php
+/*
+ * CacheException.php
+ * This file is part of Stud.IP.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Moritz Strohm <strohm@data-quest.de>
+ * @copyright   2024
+ * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
+ * @category    Stud.IP
+ * @since       6.0
+ */
+
+namespace Studip\Cache;
+
+
+/**
+ * The InvalidCacheArgumentException is an implementation of the InvalidArgumentException interface
+ *  of PSR-6 that behaves like a StudipException.
+ */
+class InvalidCacheArgumentException extends \StudipException implements \Psr\Cache\InvalidArgumentException
+{
+    //Nothing here, since there is nothing to implement.
+}
diff --git a/lib/classes/cache/Item.php b/lib/classes/cache/Item.php
new file mode 100644
index 0000000..99a6df8
--- /dev/null
+++ b/lib/classes/cache/Item.php
@@ -0,0 +1,164 @@
+<?php
+/**
+ * Item.php
+ * This file is part of Stud.IP.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * @author      Moritz Strohm <strohm@data-quest.de>
+ * @copyright   2024
+ * @license     http://www.gnu.org/licenses/gpl-2.0.html GPL version 2
+ * @category    Stud.IP
+ * @since       6.0
+ */
+
+namespace Studip\Cache;
+
+use DateInterval;
+use DateTime;
+use Psr\Cache\CacheItemInterface;
+
+/**
+ * \Studip\Cache\CacheItem implements the CacheItemInterface of PSR-6. It holds the value and the
+ * key of a cache item and also provides additional methods to get the expiration of the item.
+ */
+class Item implements CacheItemInterface
+{
+    /**
+     * @var string The key of the item in the cache.
+     */
+    protected string $key;
+
+    /**
+     * @var mixed The value of the item.
+     */
+    protected mixed $value;
+
+    /**
+     * @var DateTime|null The expiration as DateTime object or null if the expiration is not defined.
+     */
+    protected ?DateTime $expiration = null;
+
+    /**
+     * @var bool An indicator whether the item has been found in the cache (true) or not (false).
+     */
+    protected bool $cache_hit = false;
+
+    /**
+     * The constructor of \Studip\Cache\CacheItem.
+     *
+     * @param string $key The key of the item in the cache.
+     * @param mixed $value The value of the item.
+     * @param int|null $expiration The expiration of the item in seconds, if applicable.
+     * @param bool $cache_hit Whether the item shall be constructed as cache hit (true) or not (false).
+     *
+     */
+    public function __construct(
+        string $key,
+        mixed $value = null,
+        ?int $expiration = null,
+        bool $cache_hit = false
+    ) {
+        $this->key         = $key;
+        $this->value       = $value;
+        $this->cache_hit   = $cache_hit;
+        $this->expiresAfter($expiration);
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function getKey(): string
+    {
+        return $this->key;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function get(): mixed
+    {
+        return $this->value;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function isHit(): bool
+    {
+        return $this->cache_hit;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function set($value): static
+    {
+        $this->value = $value;
+        return $this;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function expiresAt($expiration): static
+    {
+        $this->expiration = $expiration;
+        return $this;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function expiresAfter($time): static
+    {
+        $this->expiration = new DateTime();
+        if ($time instanceof DateInterval) {
+            $this->expiration = $this->expiration->add($time);
+        } elseif (is_integer($time)) {
+            $this->expiration->setTimestamp(time() + $time);
+        } else {
+            $this->expiration->setTimestamp(time() + Cache::DEFAULT_EXPIRATION);
+        }
+        return $this;
+    }
+
+    // \Studip\Cache\CacheItem specific methods:
+
+    /**
+     * Sets the item to be a cache hit.
+     *
+     * @return void
+     */
+    public function setHit() : void
+    {
+        $this->cache_hit = true;
+    }
+
+    /**
+     * Returns the expiration, if set.
+     *
+     * @return DateTime|null A DateTime object with the expiration date and time
+     *     or null if the expiration is not defined.
+     */
+    public function getExpiration() : ?DateTime
+    {
+        return $this->expiration;
+    }
+
+    /**
+     * Returns the seconds from the current timestamp until the expiration of the item.
+     *
+     * @return int The seconds until the item expires
+     */
+    public function getExpirationInSeconds() : int
+    {
+        if ($this->expiration) {
+            return $this->expiration->getTimestamp() - time();
+        }
+        return 0;
+    }
+}
diff --git a/lib/classes/StudipCacheKeyTrait.php b/lib/classes/cache/KeyTrait.php
index 62eb142..021aaba 100644
--- a/lib/classes/StudipCacheKeyTrait.php
+++ b/lib/classes/cache/KeyTrait.php
@@ -1,4 +1,6 @@
 <?php
+namespace Studip\Cache;
+
 /**
  * Trait for unique cache hashes per key for each system based on db configuration which should
  * be sufficient to eliminate cache mishaps.
@@ -9,9 +11,9 @@
  * @subpackage  cache
  * @since       Stud.IP 5.0
  */
-trait StudipCacheKeyTrait
+trait KeyTrait
 {
-    protected $cache_prefix = null;
+    protected ?string $cache_prefix = null;
 
     /**
      * Returns a prefix cache key based on db configuration.
@@ -19,11 +21,11 @@ trait StudipCacheKeyTrait
      * @param  string $offset
      * @return string
      */
-    protected function getCacheKey($offset)
+    protected function getCacheKey(string $offset): string
     {
         if ($this->cache_prefix === null) {
             $this->cache_prefix = md5("{$GLOBALS['DB_STUDIP_HOST']}|{$GLOBALS['DB_STUDIP_DATABASE']}");
         }
-        return "{$this->cache_prefix}/{$offset}";
+        return "$this->cache_prefix/$offset";
     }
 }
diff --git a/lib/classes/StudipMemcachedCache.php b/lib/classes/cache/MemcachedCache.php
index 0e44dd5..1c4b685 100644
--- a/lib/classes/StudipMemcachedCache.php
+++ b/lib/classes/cache/MemcachedCache.php
@@ -1,31 +1,23 @@
 <?php
 
-/**
- * Copyright (C) 2007 - Marcus Lunzenauer <mlunzena@uos.de>
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License as
- * published by the Free Software Foundation; either version 2 of
- * the License, or (at your option) any later version.
- */
+namespace Studip\Cache;
 
+use Memcached;
+use Psr\Cache\CacheItemInterface;
 
 /**
  * Cache implementation using memcached.
  *
- * @package     studip
- * @subpackage  cache
- *
- * @author    mlunzena
+ * @author    Marcus Lunzenauer <mlunzena@uos.de>
  * @copyright (c) Authors
+ * @license GPL2 or any later version
  * @since   5.0
  */
-
-class StudipMemcachedCache implements StudipCache
+class MemcachedCache extends Cache
 {
-    use StudipCacheKeyTrait;
+    use KeyTrait;
 
-    private $memcache;
+    private Memcached $memcache;
 
     /**
      * @return string A translateable display name for this cache class.
@@ -38,18 +30,18 @@ class StudipMemcachedCache implements StudipCache
     public function __construct($servers)
     {
         if (!extension_loaded('memcached')) {
-            throw new Exception('Memcache extension missing.');
+            throw new \Exception('Memcache extension missing.');
         }
 
-        $prefix = Config::get()->STUDIP_INSTALLATION_ID;
-        $this->memcache = new Memcached('studip' . $prefix ? '-' . $prefix : '');
+        $prefix = \Config::get()->STUDIP_INSTALLATION_ID;
+        $this->memcache = new Memcached('studip' . ($prefix ? '-' . $prefix : ''));
 
         if (count($this->memcache->getServerList()) === 0) {
             foreach ($servers as $server) {
                 $status = $this->memcache->addServer($server['hostname'], (int) $server['port']);
 
                 if (!$status) {
-                    throw new Exception("Could not add server: {$server['hostname']} @ port {$server['port']}");
+                    throw new \Exception("Could not add server: {$server['hostname']} @ port {$server['port']}");
                 }
             }
         }
@@ -81,40 +73,6 @@ class StudipMemcachedCache implements StudipCache
     }
 
     /**
-     * Retrieve item from the server.
-     *
-     * Example:
-     *
-     *   # reads foo
-     *   $foo = $cache->reads('foo');
-     *
-     * @param   string $arg a single key
-     * @returns mixed  the previously stored data if an item with such a key
-     *                 exists on the server or FALSE on failure.
-     */
-    public function read($arg)
-    {
-        $key = $this->getCacheKey($arg);
-        return $this->memcache->get($key);
-    }
-
-    /**
-     * Store data at the server.
-     *
-     * @param string $arg the item's key.
-     * @param string $content the item's content.
-     * @param int $expire the item's expiry time in seconds. Defaults to 12h.
-     *
-     * @returns mixed  returns TRUE on success or FALSE on failure.
-     *
-     */
-    public function write($arg, $content, $expire = self::DEFAULT_EXPIRATION)
-    {
-        $key = $this->getCacheKey($arg);
-        return $this->memcache->set($key, $content, $expire);
-    }
-
-    /**
      * Return statistics.
      *
      * @StudipCache::getStats()
@@ -123,20 +81,19 @@ class StudipMemcachedCache implements StudipCache
      */
     public function getStats(): array
     {
-        $stats = $this->memcache->getStats();
-        return $stats;
+        return $this->memcache->getStats();
     }
 
     /**
      * Return the Vue component name and props that handle configuration.
      *
-     * @see StudipCache::getConfig()
+     * @see Cache::getConfig()
      *
      * @return array
      */
     public static function getConfig(): array
     {
-        $currentCache = Config::get()->SYSTEMCACHE;
+        $currentCache = \Config::get()->SYSTEMCACHE;
 
         // Set default config for this cache
         $currentConfig = [
@@ -154,4 +111,41 @@ class StudipMemcachedCache implements StudipCache
         ];
     }
 
+    /**
+     * @inheritDoc
+     */
+    public function getItem(string $key): CacheItemInterface
+    {
+        $item = new Item($key);
+        $value = $this->memcache->get($this->getCacheKey($key));
+        if ($this->memcache->getResultCode() !== Memcached::RES_NOTFOUND) {
+            // Set the value, even if it is the boolean value false:
+            $item->setHit();
+            $item->set($value);
+        }
+        return $item;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function hasItem(string $key): bool
+    {
+        return $this->memcache->checkKey($this->getCacheKey($key));
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function save(CacheItemInterface $item): bool
+    {
+        $expiration = $this->getExpiration($item);
+        if ($expiration < 1) {
+            // The item would expire immediately.
+            return false;
+        }
+
+        $real_key = $this->getCacheKey($item->getKey());
+        return $this->memcache->set($real_key, $item->get(), $expiration);
+    }
 }
diff --git a/lib/classes/cache/MemoryCache.php b/lib/classes/cache/MemoryCache.php
new file mode 100644
index 0000000..7c00753
--- /dev/null
+++ b/lib/classes/cache/MemoryCache.php
@@ -0,0 +1,98 @@
+<?php
+
+namespace Studip\Cache;
+
+use DateTime;
+use Psr\Cache\CacheItemInterface;
+
+/**
+ * The php memory implementation of the StudipCache interface.
+ *
+ * @author  Jan-Hendrik Willms <tleilax+studip@gmail.com>
+ * @license GPL2 or any later version
+ * @since   Stud.IP 5.0
+ */
+class MemoryCache extends Cache
+{
+    protected array $memory_cache = [];
+
+    /**
+     * Expires just a single key.
+     *
+     * @param  string $arg the key
+     */
+    public function expire($arg)
+    {
+        unset($this->memory_cache[$arg]);
+    }
+
+    /**
+     * Expire all items from the cache.
+     */
+    public function flush()
+    {
+        $this->memory_cache = [];
+    }
+
+    public static function getDisplayName(): string
+    {
+        return 'Memory cache';
+    }
+
+    public function getStats(): array
+    {
+        return [];
+    }
+
+    public static function getConfig(): array
+    {
+        return [];
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function getItem(string $key): CacheItemInterface
+    {
+        $item = new Item($key);
+        if (!isset($this->memory_cache[$key])) {
+            return $item;
+        }
+        if ($this->memory_cache[$key]['expires'] < time()) {
+            $this->expire($key);
+            return $item;
+        }
+        $item->setHit();
+        $item->set($this->memory_cache[$key]['data']);
+        if (!empty($this->memory_cache[$key]['expires'])) {
+            $expiration = new DateTime();
+            $expiration->setTimestamp($this->memory_cache[$key]['expires']);
+            $item->expiresAt($expiration);
+        }
+        return $item;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function hasItem(string $key): bool
+    {
+        return isset($this->memory_cache[$key])
+            && $this->memory_cache[$key]['expires'] < time();
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function save(CacheItemInterface $item): bool
+    {
+        $expiration = $this->getExpiration($item);
+
+        $this->memory_cache[$item->getKey()] = [
+            'expires' => $expiration + time(),
+            'data'    => $item->get(),
+        ];
+
+        return true;
+    }
+}
diff --git a/lib/classes/StudipCacheProxy.php b/lib/classes/cache/Proxy.php
index 686f812..fef034d 100644
--- a/lib/classes/StudipCacheProxy.php
+++ b/lib/classes/cache/Proxy.php
@@ -1,4 +1,10 @@
 <?php
+
+namespace Studip\Cache;
+
+use Psr\Cache\CacheItemInterface;
+use StudipCacheOperation;
+
 /**
  * Proxies a StudipCache and stores the expire operation in the database.
  * These operations are lateron applied to the cache they should have
@@ -8,18 +14,18 @@
  * @license GPL2 or any later version
  * @since   Stud.IP 3.3
  */
-class StudipCacheProxy implements StudipCache
+class Proxy extends Cache
 {
-    protected $actual_cache;
-    protected $proxy_these;
+    protected Cache $actual_cache;
+    protected array $proxy_these;
 
     /**
-     * @param StudipCache $cache       The actual cache object
-     * @param mixed       $proxy_these List of operations to proxy (should be
-     *                                 an array but a space seperated string
-     *                                 is also valid)
+     * @param Cache $cache       The actual cache object
+     * @param mixed $proxy_these List of operations to proxy (should be an
+     *                           array but a space seperated string is also
+     *                           valid)
      */
-    public function __construct(StudipCache $cache, $proxy_these = ['expire'])
+    public function __construct(Cache $cache, $proxy_these = ['expire'])
     {
         if (!is_array($proxy_these)) {
             $proxy_these = words($proxy_these);
@@ -34,20 +40,20 @@ class StudipCacheProxy implements StudipCache
     /**
      * Expires just a single key.
      *
-     * @param string $key The item's key
+     * @param string $arg The item's key
      */
-    public function expire($key)
+    public function expire($arg)
     {
         if (in_array('expire', $this->proxy_these)) {
             try {
-                $operation = new StudipCacheOperation([$key, 'expire']);
+                $operation = new StudipCacheOperation([$arg, 'expire']);
                 $operation->parameters = serialize([]);
                 $operation->store();
-            } catch (Exception $e) {
+            } catch (\Exception) {
             }
         }
 
-        return $this->actual_cache->expire($key);
+        return $this->actual_cache->expire($arg);
     }
 
     /**
@@ -60,58 +66,58 @@ class StudipCacheProxy implements StudipCache
                 $operation = new StudipCacheOperation(['', 'flush']);
                 $operation->parameters = serialize([]);
                 $operation->store();
-            } catch (Exception $e) {
+            } catch (\Exception) {
             }
         }
 
         return $this->actual_cache->flush();
     }
 
-    /**
-     * Reads just a single key from the cache.
-     *
-     * @param  string $key The item's key
-     * @return mixed The corresponding value
-     */
-    public function read($key)
+    public static function getDisplayName(): string
     {
-        return $this->actual_cache->read($key);
+        return static::class;
     }
 
-    /**
-     * Store data at the server.
-     *
-     * @param string $key     The item's key
-     * @param string $content The item's conten
-     * @param int    $expires The item's expiry time in seconds, defaults to 12h
-     * @return bool  Returns TRUE on success or FALSE on failure
-     */
-    public function write($key, $content, $expires = self::DEFAULT_EXPIRATION)
+    public function getStats(): array
     {
-        if (in_array('write', $this->proxy_these)) {
-            try {
-                $operation = new StudipCacheOperation([$key, 'write']);
-                $operation->parameters = serialize([$content, $expires]);
-                $operation->store();
-            } catch (Exception $e) {
-            }
-        }
+        return $this->actual_cache->getStats();
+    }
 
-        return $this->actual_cache->write($key, $content, $expires);
+    public static function getConfig(): array
+    {
+        return [];
     }
 
-    public static function getDisplayName(): string
+    /**
+     * @inheritDoc
+     */
+    public function getItem(string $key): CacheItemInterface
     {
-        return static::class;
+        return $this->actual_cache->getItem($key);
     }
 
-    public function getStats(): array
+    /**
+     * @inheritDoc
+     */
+    public function hasItem(string $key): bool
     {
-        return $this->actual_cache->getStats();
+        return $this->actual_cache->hasItem($key);
     }
 
-    public static function getConfig(): array
+    /**
+     * @inheritDoc
+     */
+    public function save(CacheItemInterface $item): bool
     {
-        return [];
+        if (in_array('save', $this->proxy_these)) {
+            try {
+                $operation = new StudipCacheOperation([$item->getKey(), 'save']);
+                $operation->parameters = serialize([$item]);
+                $operation->store();
+            } catch (\Exception) {
+            }
+        }
+
+        return $this->actual_cache->save($item);
     }
 }
diff --git a/lib/classes/StudipRedisCache.class.php b/lib/classes/cache/RedisCache.php
index 7b9570b..a78f751 100644
--- a/lib/classes/StudipRedisCache.class.php
+++ b/lib/classes/cache/RedisCache.php
@@ -1,4 +1,15 @@
 <?php
+
+namespace Studip\Cache;
+
+use BadMethodCallException;
+use Config;
+use DateTime;
+use Exception;
+use Psr\Cache\CacheItemInterface;
+use Redis;
+use RedisException;
+
 /**
  * Cache implementation using redis.
  *
@@ -8,9 +19,9 @@
  * @subpackage  cache
  * @since       Stud.IP 5.0
  */
-class StudipRedisCache implements StudipCache
+class RedisCache extends Cache
 {
-    use StudipCacheKeyTrait;
+    use KeyTrait;
 
     private $redis;
 
@@ -28,6 +39,8 @@ class StudipRedisCache implements StudipCache
      * @param string $hostname Hostname of redis server
      * @param int    $port     Port of redis server
      * @param string $auth     Optional auth token/password
+     *
+     * @throws RedisException
      */
     public function __construct($hostname, $port, string $auth = '')
     {
@@ -74,41 +87,6 @@ class StudipRedisCache implements StudipCache
     }
 
     /**
-     * Retrieve item from the server.
-     *
-     * Example:
-     *
-     *   # reads foo
-     *   $foo = $cache->reads('foo');
-     *
-     * @param  string $arg a single key
-     * @return mixed  the previously stored data if an item with such a key
-     *                exists on the server or FALSE on failure.
-     */
-    public function read($arg)
-    {
-        $key = $this->getCacheKey($arg);
-
-        $result = $this->redis->get($key);
-
-        return ($result === null) ? null : unserialize($result);
-    }
-
-    /**
-     * Store data at the server.
-     *
-     * @param string   the item's key.
-     * @param string   the item's content.
-     * @param int      the item's expiry time in seconds. Defaults to 12h.
-     * @return mixed  returns TRUE on success or FALSE on failure.
-     */
-    public function write($name, $content, $expire = self::DEFAULT_EXPIRATION)
-    {
-        $key = $this->getCacheKey($name);
-        return $this->redis->setEx($key, $expire, serialize($content));
-    }
-
-    /**
      * Expire all items from the cache.
      */
     public function flush()
@@ -174,4 +152,47 @@ class StudipRedisCache implements StudipCache
             'props' => $currentConfig
         ];
     }
+
+    /**
+     * @inheritDoc
+     */
+    public function getItem(string $key): CacheItemInterface
+    {
+        $item = new Item($key);
+        $real_key = $this->getCacheKey($key);
+        $result = $this->redis->get($real_key);
+        if ($result === null) {
+            return $item;
+        }
+        $item->setHit();
+        $item->set(unserialize($result));
+        $expiration = new DateTime();
+        $expiration->setTimestamp($this->redis->expiretime($real_key));
+        $item->expiresAt($expiration);
+        return $item;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function hasItem(string $key): bool
+    {
+        $real_key = $this->getCacheKey($key);
+        return $this->redis->get($real_key) !== null;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function save(CacheItemInterface $item): bool
+    {
+        $expiration = $this->getExpiration($item);
+        if ($expiration < 1) {
+            // The item would expire immediately.
+            return false;
+        }
+
+        $real_key = $this->getCacheKey($item->getKey());
+        return $this->redis->setEx($real_key, $expiration, serialize($item->get()));
+    }
 }
diff --git a/lib/classes/StudipCacheWrapper.php b/lib/classes/cache/Wrapper.php
index 6c75c01..4e6342c 100644
--- a/lib/classes/StudipCacheWrapper.php
+++ b/lib/classes/cache/Wrapper.php
@@ -1,5 +1,9 @@
 <?php
 
+namespace Studip\Cache;
+
+use Psr\Cache\CacheItemInterface;
+
 /**
  * The cache wrapper wraps a memory cache around another cache. This should
  * reduce the accesses to the actual cache.
@@ -8,17 +12,15 @@
  * @license GPL2 or any later version
  * @since Stud.IP 5.4
  */
-class StudipCacheWrapper implements StudipCache
+class Wrapper extends Cache
 {
-    const DEFAULT_MEMORY_EXPIRATION = 60;
-
-    protected $actual_cache;
-    protected $memory_cache;
+    protected Cache $actual_cache;
+    protected MemoryCache $memory_cache;
 
-    public function __construct(StudipCache $actual_cache)
+    public function __construct(Cache $actual_cache)
     {
         $this->actual_cache = $actual_cache;
-        $this->memory_cache = new StudipMemoryCache();
+        $this->memory_cache = new MemoryCache();
     }
 
     /**
@@ -39,47 +41,55 @@ class StudipCacheWrapper implements StudipCache
         $this->actual_cache->flush();
     }
 
+    public static function getDisplayName(): string
+    {
+        return static::class;
+    }
+
+    public function getStats(): array
+    {
+        return $this->actual_cache->getStats();
+    }
+
+    public static function getConfig(): array
+    {
+        return [];
+    }
+
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
-    public function read($arg)
+    public function getItem(string $key): CacheItemInterface
     {
-        $cached = $this->memory_cache->read($arg);
-        if ($cached !== false) {
+        $cached = $this->memory_cache->getItem($key);
+        if ($cached->isHit()) {
             return $cached;
         }
 
-        $cached = $this->actual_cache->read($arg);
-        if ($cached !== false) {
-            $this->memory_cache->write($arg, $cached, self::DEFAULT_MEMORY_EXPIRATION);
+        $cached = $this->actual_cache->getItem($key);
+        if ($cached->isHit()) {
+            $this->memory_cache->save($cached);
         }
         return $cached;
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
-    public function write($name, $content, $expires = self::DEFAULT_EXPIRATION)
+    public function hasItem(string $key): bool
     {
-        if ($this->actual_cache->write($name, $content, $expires)) {
-            return $this->memory_cache->write($name, $content, $expires);
-        } else {
-            return false;
-        }
-    }
-
-    public static function getDisplayName(): string
-    {
-        return static::class;
-    }
-
-    public function getStats(): array
-    {
-        return $this->actual_cache->getStats();
+        return $this->actual_cache->hasItem($key);
     }
 
-    public static function getConfig(): array
+    /**
+     * @inheritDoc
+     */
+    public function save(CacheItemInterface $item): bool
     {
-        return [];
+        if ($this->actual_cache->save($item)) {
+            return $this->memory_cache->save($item);
+        } else {
+            return false;
+        }
     }
 }
diff --git a/lib/classes/calendar/CalendarScheduleModel.php b/lib/classes/calendar/CalendarScheduleModel.php
index 468b7e2..0aeadee 100644
--- a/lib/classes/calendar/CalendarScheduleModel.php
+++ b/lib/classes/calendar/CalendarScheduleModel.php
@@ -623,7 +623,7 @@ class CalendarScheduleModel
                     SET visible = 0
                     WHERE seminar_id = ? AND user_id = ? AND metadate_id = ?");
             } else {
-                $stmt = DBManager::get()->prepare("INSERT INTO schedule_seminare
+                $stmt = DBManager::get()->prepare("INSERT IGNORE INTO schedule_seminare
                     (seminar_id, user_id, metadate_id, visible)
                     VALUES(?, ?, ?, 0)");
             }
diff --git a/lib/classes/calendar/EventData.class.php b/lib/classes/calendar/EventData.php
index 95e89b0..95e89b0 100644
--- a/lib/classes/calendar/EventData.class.php
+++ b/lib/classes/calendar/EventData.php
diff --git a/lib/classes/calendar/EventSource.interface.php b/lib/classes/calendar/EventSource.php
index 48506d7..48506d7 100644
--- a/lib/classes/calendar/EventSource.interface.php
+++ b/lib/classes/calendar/EventSource.php
diff --git a/lib/classes/calendar/ICalendarExport.class.php b/lib/classes/calendar/ICalendarExport.php
index ce50f87..d8d1af7 100644
--- a/lib/classes/calendar/ICalendarExport.class.php
+++ b/lib/classes/calendar/ICalendarExport.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * ICalendarExport.class.php
+ * ICalendarExport.php
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -55,7 +55,7 @@ class ICalendarExport
                     (`calendar_dates`.`begin` <= :end
                         AND `calendar_dates`.`end` >= :begin)
                     OR (`calendar_dates`.`repetition_type` != 'SINGLE'
-                        AND (`calendar_dates`.`repetition_end` >= :end
+                        AND (`calendar_dates`.`repetition_end` >= :begin
                             OR `calendar_dates`.`repetition_end` = 0)
                     AND `calendar_dates`.`begin` < :end))",
             [
@@ -76,20 +76,7 @@ class ICalendarExport
         if ($this->time === 0) {
             $this->time = time();
         }
-        $dates = CourseDate::findBySql(
-            "LEFT JOIN `seminar_user`
-                ON `termine`.`range_id` = `seminar_user`.`Seminar_id`
-            WHERE
-                `seminar_user`.`user_id` = :user_id
-                AND `seminar_user`.`bind_calendar` = 1
-                AND (`termine`.`date` <= :end
-                    AND `termine`.`end_time` >= :begin)",
-            [
-                ':user_id'  => $user_id,
-                ':begin'    => $start->getTimestamp(),
-                ':end'      => $end->getTimestamp(),
-            ]
-        );
+        $dates = CalendarCourseDate::getEvents($start, $end, $user_id);
         $ical = '';
         foreach ($dates as $date) {
             $ical .= $this->writeICalEvent($this->prepareCourseDate($date));
@@ -102,20 +89,7 @@ class ICalendarExport
         if ($this->time === 0) {
             $this->time = time();
         }
-        $dates = CourseExDate::findBySql(
-            "LEFT JOIN `seminar_user`
-                ON `ex_termine`.`range_id` = `seminar_user`.`Seminar_id`
-            WHERE
-                `seminar_user`.`user_id` = :user_id
-                AND `seminar_user`.`bind_calendar` = 1
-                AND (`ex_termine`.`date` <= :end
-                    AND `ex_termine`.`end_time` >= :begin)",
-            [
-                ':user_id'  => $user_id,
-                ':begin'    => $start->getTimestamp(),
-                ':end'      => $end->getTimestamp(),
-            ]
-        );
+        $dates = CalendarCourseExDate::getEvents($start, $end, $user_id);
         $ical = '';
         foreach ($dates as $date) {
             $ical .= $this->writeICalEvent($this->prepareCourseDate($date));
@@ -124,10 +98,10 @@ class ICalendarExport
     }
 
     /**
-     * @param CalendarDate | CourseExDate $date
-     * @return array
+     * @param CalendarDate $date The calendar date to export.
+     * @return array Calendar date data prepared for export.
      */
-    public function prepareCalendarDate($date): array
+    public function prepareCalendarDate(CalendarDate $date): array
     {
         return [
             'SUMMARY'       => $date->title,
@@ -155,8 +129,8 @@ class ICalendarExport
     }
 
     /**
-     * @param CalendarDate | CourseExDate $date
-     * @return array
+     * @param CourseDate | CourseExDate $date The course date to export.
+     * @return array Course date data prepared for export.
      */
     public function prepareCourseDate($date): array
     {
@@ -165,10 +139,13 @@ class ICalendarExport
         if ($date instanceof CourseExDate) {
             $summary .= ' ' . _('(fällt aus)');
             $categories = '';
+            $description = $date->content;
+        } else {
+            $description = implode("\n", $date->topics->pluck('title'));
         }
         return [
             'SUMMARY'       => $summary,
-            'DESCRIPTION'   => '',
+            'DESCRIPTION'   => $description,
             'LOCATION'      => $date->getRoomName(),
             'CATEGORIES'    => $categories,
             'LAST-MODIFIED' => $date->chdate,
@@ -286,7 +263,7 @@ class ICalendarExport
                 case 'DUE':
                 case 'RECURRENCE-ID':
                     if (array_key_exists('VALUE', $params)) {
-                        if ($params['VALUE'] == 'DATE') {
+                        if ($params['VALUE'] === 'DATE') {
                             $value = $this->_exportDate($value);
                         } else {
                             $value = $this->_exportDateTime($value);
@@ -299,12 +276,12 @@ class ICalendarExport
                     break;
 
                 case 'EXDATE':
-                    if (array_key_exists('VALUE', $params)) {
+                    if (array_key_exists('VALUE', $params) && $params['VALUE'] === 'DATE') {
                         $value = $this->exportExDate($value);
                     } else {
-                        $value = $this->exportExDateTime($value);
+                        $value = $this->exportExDateTime($value, $exdate_time);
+                        $params_str = ';TZID=Europe/Berlin';
                     }
-                    $params_str = ';TZID=Europe/Berlin';
                     break;
 
                 // Integer fields
@@ -338,7 +315,7 @@ class ICalendarExport
                 // Recursion fields
                 case 'EXRULE':
                 case 'RRULE':
-                    if ($value['type'] !== 'SINGLE') {
+                    if ($value['type'] !== 'SINGLE' && $value['type'] !== '') {
                         $value = $this->_exportRecurrence($value);
                     }
                     break;
@@ -381,8 +358,8 @@ class ICalendarExport
     public function _exportDateTime($value, $utc = false)
     {
         $date_time = new DateTime();
-        $date_time->setTimestamp($value);
-        //transform local time in UTC
+        $date_time->setTimestamp(intval($value));
+        //transform local time to UTC
         if ($utc) {
             $tz_utc = new DateTimeZone('UTC');
             $date_time->setTimezone($tz_utc);
@@ -427,7 +404,7 @@ class ICalendarExport
             $value['offset'] = '-1';
         }
 
-        if ($value['count']) {
+        if ($value['count'] > 1) {
             unset($value['expire']);
         }
 
@@ -438,7 +415,7 @@ class ICalendarExport
                         $rrule[] = 'FREQ=' . $r_value;
                         break;
                     case 'expire':
-                        if ($r_value < CalendarDate::NEVER_ENDING)
+                        if ($r_value)
                             $rrule[] = 'UNTIL=' . $this->_exportDateTime($r_value, true);
                         break;
                     case 'interval':
@@ -470,7 +447,9 @@ class ICalendarExport
                         $rrule[] = 'BYMONTH=' . $r_value;
                         break;
                     case 'count':
-                        $rrule[] = 'COUNT=' . $r_value;
+                        if ($r_value > 1) {
+                            $rrule[] = 'COUNT=' . $r_value;
+                        }
                         break;
                 }
             }
@@ -501,35 +480,40 @@ class ICalendarExport
         return implode(',', $wdays);
     }
 
+
     /**
      * Formats dates of exception.
      *
-     * @param string $value Unix timestamps as csv list.
+     * @param string $value Date values (Y-m-d) as csv list.
      * @return string The formatted Exceptions.
      */
     public function exportExDate(string $value): string
     {
-        $exdates = [];
-        $date_times = explode(',', $value);
-        foreach ($date_times as $date_time) {
-            $exdates[] = $this->_exportDate($date_time);
+        $ex_dates = [];
+        $dates = explode(',', $value);
+        foreach ($dates as $date) {
+            $ex_datetime = $date . ' 12:00:00';
+            $ex_date = DateTime::createFromFormat('Y-m-d H:i:s', $ex_datetime);
+            $ex_dates[] = $this->_exportDate($ex_date->getTimestamp());
         }
-        return implode(',', $exdates);
+
+        return implode(',', $ex_dates);
     }
 
     /**
      * Formats date times of exception.
      *
-     * @param string $value Unix timestamps as csv list.
+     * @param string $value Date values (Y-m-d) as csv list.
+     * @param int $begin Start date of event as unix timestamp.
      * @return string The formatted Exceptions.
      */
-    public function exportExDateTime(string $value): string
+    public function exportExDateTime(string $value, int $begin): string
     {
         $ex_dates = [];
-        $ex_date_times = explode(',', $value);
-        foreach ($ex_date_times as $ex_date_time) {
-            $date_time = new DateTime();
-            $date_time->setTimestamp($ex_date_time);
+        $dates = explode(',', $value);
+        foreach ($dates as $date) {
+            $ex_datetime = $date . date(' H:i:s', $begin);
+            $date_time = DateTime::createFromFormat('Y-m-d H:i:s', $ex_datetime);
             $ex_dates[] = $date_time->format('Ymd\THis');
         }
         return implode(',', $ex_dates);
diff --git a/lib/classes/calendar/ICalendarImport.class.php b/lib/classes/calendar/ICalendarImport.php
index e78696d..e78696d 100644
--- a/lib/classes/calendar/ICalendarImport.class.php
+++ b/lib/classes/calendar/ICalendarImport.php
diff --git a/lib/classes/calendar/Owner.interface.php b/lib/classes/calendar/Owner.php
index a7c2519..a7c2519 100644
--- a/lib/classes/calendar/Owner.interface.php
+++ b/lib/classes/calendar/Owner.php
diff --git a/lib/classes/cas/CAS_PGTStorage_Cache.php b/lib/classes/cas/CAS_PGTStorage_Cache.php
index 284b591..61ce9fa 100644
--- a/lib/classes/cas/CAS_PGTStorage_Cache.php
+++ b/lib/classes/cas/CAS_PGTStorage_Cache.php
@@ -43,7 +43,7 @@ class CAS_PGTStorage_Cache extends CAS_PGTStorage_AbstractStorage
      */
     public function write($pgt, $pgt_iou)
     {
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         $cache_key = 'pgtiou/' . $pgt_iou;
         return $cache->write($cache_key, $pgt);
     }
@@ -58,7 +58,7 @@ class CAS_PGTStorage_Cache extends CAS_PGTStorage_AbstractStorage
      */
     public function read($pgt_iou)
     {
-        $cache = StudipCacheFactory::getCache();
+        $cache = \Studip\Cache\Factory::getCache();
         $cache_key = 'pgtiou/' . $pgt_iou;
         $pgt = $cache->read($cache_key);
         $cache->expire($cache_key);
diff --git a/lib/classes/coursewizardsteps/AdvancedBasicDataWizardStep.php b/lib/classes/coursewizardsteps/AdvancedBasicDataWizardStep.php
index 780f837..cd33fd3 100644
--- a/lib/classes/coursewizardsteps/AdvancedBasicDataWizardStep.php
+++ b/lib/classes/coursewizardsteps/AdvancedBasicDataWizardStep.php
@@ -36,7 +36,7 @@ class AdvancedBasicDataWizardStep extends BasicDataWizardStep
         }
 
         // Load template from step template directory.
-        $factory = new Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'].'/app/views/course/wizard/steps');
+        $factory = new Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'].'/app/views/course/wizard/steps');
         $template = $factory->open('advancedbasicdata/index');
 
         $template = $this->setupTemplateAttributes($template, $values, $stepnumber, $temp_id);
diff --git a/lib/classes/coursewizardsteps/BasicDataWizardStep.php b/lib/classes/coursewizardsteps/BasicDataWizardStep.php
index 4f424e8..d47c4f3 100644
--- a/lib/classes/coursewizardsteps/BasicDataWizardStep.php
+++ b/lib/classes/coursewizardsteps/BasicDataWizardStep.php
@@ -28,7 +28,7 @@ class BasicDataWizardStep implements CourseWizardStep
     public function getStepTemplate($values, $stepnumber, $temp_id)
     {
         // Load template from step template directory.
-        $factory = new Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views/course/wizard/steps');
+        $factory = new Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views/course/wizard/steps');
         if (!empty($values[__CLASS__]['studygroup'])) {
             $tpl = $factory->open('basicdata/index_studygroup');
             $values[__CLASS__]['lecturers'][$GLOBALS['user']->id] = 1;
@@ -356,9 +356,9 @@ class BasicDataWizardStep implements CourseWizardStep
                 htmlReady(get_title_for_status('dozent', 1, $values['coursetype']))
             );
         }
-        if (!$values['lecturers'][$GLOBALS['user']->id] && !$GLOBALS['perm']->have_perm('admin')) {
+        if (empty($values['lecturers'][$GLOBALS['user']->id]) && !$GLOBALS['perm']->have_perm('admin')) {
             if (Config::get()->DEPUTIES_ENABLE) {
-                if (!$values['deputies'][$GLOBALS['user']->id]) {
+                if (empty($values['deputies'][$GLOBALS['user']->id])) {
                     $errors[] = sprintf(
                         _('Sie selbst müssen entweder als %s oder als Vertretung eingetragen sein.'),
                         htmlReady(get_title_for_status('dozent', 1, $values['coursetype']))
@@ -620,7 +620,10 @@ class BasicDataWizardStep implements CourseWizardStep
 
                 }
             }
-
+        } else {
+            foreach ($indices as $index) {
+                $values[$index] = $values[$index] ?? '';
+            }
         }
 
         return $values;
diff --git a/lib/classes/coursewizardsteps/LVGroupsWizardStep.php b/lib/classes/coursewizardsteps/LVGroupsWizardStep.php
index 22f11ea..c651714 100644
--- a/lib/classes/coursewizardsteps/LVGroupsWizardStep.php
+++ b/lib/classes/coursewizardsteps/LVGroupsWizardStep.php
@@ -13,7 +13,7 @@
  * @category    Stud.IP
  */
 
-require_once dirname(__FILE__) . '/../StudipLvgruppeSelection.class.php';
+require_once dirname(__FILE__) . '/../StudipLvgruppeSelection.php';
 
 class LVGroupsWizardStep implements CourseWizardStep
 {
@@ -36,10 +36,10 @@ class LVGroupsWizardStep implements CourseWizardStep
         $course_start_time = $values[$step_one_class]['start_time'];
 
         // We only need our own stored values here.
-        $values = $values[__CLASS__];
+        $values = $values[__CLASS__] ?? [];
 
         // Load template from step template directory.
-        $factory = new Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views/course/wizard/steps');
+        $factory = new Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views/course/wizard/steps');
         $tpl = $factory->open('lvgroups/index');
         $tpl->set_attribute('values', $values);
 
@@ -53,9 +53,12 @@ class LVGroupsWizardStep implements CourseWizardStep
             }
         }
 
-        $selection_details = $values['lvgruppe_selection']['area_details'];
+        $selection_details = $values['lvgruppe_selection']['area_details'] ?? null;
 
-        if ($_SESSION[__CLASS__]['course_start_time'] != $course_start_time) {
+        if (
+            isset($_SESSION[__CLASS__]['course_start_time'])
+            && $_SESSION[__CLASS__]['course_start_time'] != $course_start_time
+        ) {
             // don't store previously opened nodes
             // because we get in trouble if the semester has changed
             $open_nodes = [];
@@ -65,15 +68,15 @@ class LVGroupsWizardStep implements CourseWizardStep
 
         $_SESSION[__CLASS__]['course_start_time'] = $course_start_time;
 
-        $tpl->set_attribute('open_lvg_nodes', $open_nodes);
-        $tpl->set_attribute('selection', $selection);
-        $tpl->set_attribute('selection_details', $selection_details);
-        $tpl->set_attribute('tree', $lvgtree->getRootItem()->getChildren());
+        $tpl->open_lvg_nodes = $open_nodes;
+        $tpl->selection = $selection;
+        $tpl->selection_details = $selection_details;
+        $tpl->tree = $lvgtree->getRootItem()->getChildren();
 
-        $tpl->set_attribute('ajax_url', $values['ajax_url'] ?: URLHelper::getLink('dispatch.php/course/wizard/ajax'));
-        $tpl->set_attribute('no_js_url', $values['no_js_url'] ?: 'dispatch.php/course/wizard/forward/'.$stepnumber.'/'.$temp_id);
-        $tpl->set_attribute('stepnumber', $stepnumber);
-        $tpl->set_attribute('temp_id', $temp_id);
+        $tpl->ajax_url = !empty($values['ajax_url']) ? $values['ajax_url'] : URLHelper::getLink('dispatch.php/course/wizard/ajax');
+        $tpl->no_js_url = !empty($values['no_js_url']) ? $values['no_js_url'] : URLHelper::getURL('dispatch.php/course/wizard/forward/'.$stepnumber.'/'.$temp_id);
+        $tpl->stepnumber = $stepnumber;
+        $tpl->temp_id = $temp_id;
         return $tpl->render();
     }
 
@@ -223,7 +226,7 @@ class LVGroupsWizardStep implements CourseWizardStep
                 continue;
             }
 
-            $factory = new Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views');
+            $factory = new Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views');
             $html = $factory->render('course/wizard/steps/lvgroups/lvgroup_searchentry', compact('area'));
             $data = [
                 'id' => $area->id,
@@ -285,7 +288,7 @@ class LVGroupsWizardStep implements CourseWizardStep
             'Studiengang']);
         $pathes = ModuleManagementModelTreeItem::getPathes($trails);
 
-        $factory = new Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views');
+        $factory = new Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views');
         $html = $factory->render('course/lvgselector/entry_trails',
                 compact('area', 'pathes'));
 
@@ -305,7 +308,7 @@ class LVGroupsWizardStep implements CourseWizardStep
         $mvvid = explode('-', $id);
         $area = Lvgruppe::find($mvvid[0]);
 
-        $factory = new Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views');
+        $factory = new Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'] . '/app/views');
         $html = $factory->render('course/wizard/steps/lvgroups/lvgroup_entry', ['area' => $area, 'locked' => false, 'course_id' => '']);
 
         $data = [
diff --git a/lib/classes/coursewizardsteps/StudyAreasWizardStep.php b/lib/classes/coursewizardsteps/StudyAreasWizardStep.php
index f81ce41..eac7e37 100644
--- a/lib/classes/coursewizardsteps/StudyAreasWizardStep.php
+++ b/lib/classes/coursewizardsteps/StudyAreasWizardStep.php
@@ -28,9 +28,9 @@ class StudyAreasWizardStep implements CourseWizardStep
     public function getStepTemplate($values, $stepnumber, $temp_id)
     {
         // We only need our own stored values here.
-        $values = $values[get_class($this)];
+        $values = $values[get_class($this)] ?? [];
         // Load template from step template directory.
-        $factory = new Flexi_TemplateFactory($GLOBALS['STUDIP_BASE_PATH'].'/app/views/course/wizard/steps');
+        $factory = new Flexi\Factory($GLOBALS['STUDIP_BASE_PATH'].'/app/views/course/wizard/steps');
         $tpl = $factory->open('studyareas/index');
         if (!empty($values['studyareas'])) {
             $tree = $this->buildPartialSemTree(StudipStudyArea::backwards(StudipStudyArea::findMany($values['studyareas'])));
diff --git a/lib/classes/exportdocument/ExportDocument.interface.php b/lib/classes/exportdocument/ExportDocument.php
index 27aaee2..27aaee2 100644
--- a/lib/classes/exportdocument/ExportDocument.interface.php
+++ b/lib/classes/exportdocument/ExportDocument.php
diff --git a/lib/classes/exportdocument/ExportPDF.class.php b/lib/classes/exportdocument/ExportPDF.php
index 8645f5b..f676c45 100644
--- a/lib/classes/exportdocument/ExportPDF.class.php
+++ b/lib/classes/exportdocument/ExportPDF.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /**
- * ExportPDF.class.php - create and export or save a pdf with simple HTML-Data
+ * ExportPDF.php - create and export or save a pdf with simple HTML-Data
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -115,12 +115,15 @@ class ExportPDF extends TCPDF implements ExportDocument
             // Fetch headers from url, handle possible redirects
             do {
                 $headers = get_headers($url, true, get_default_http_stream_context($url));
+                if (!$headers) {
+                    break;
+                }
                 list(, $status) = explode(' ', $headers[0]);
 
                 $url = $headers['Location'] ?? $headers['location'] ?? $url;
             } while (in_array($status, [300, 301, 302, 303, 305, 307]));
 
-            $status = $status ?: 404;
+            $status = $status ?? 404;
 
             // Replace image with link on error (and not internal), otherwise return sainitized
             // url
diff --git a/lib/classes/forms/Captcha.php b/lib/classes/forms/Captcha.php
new file mode 100644
index 0000000..c01b702
--- /dev/null
+++ b/lib/classes/forms/Captcha.php
@@ -0,0 +1,29 @@
+<?php
+
+namespace Studip\Forms;
+
+use CaptchaChallenge;
+
+/**
+ * The Text class represents a part of a form that displays a captcha.
+ */
+class Captcha extends Fieldset
+{
+    private CaptchaInput $captcha_input;
+
+    public function __construct()
+    {
+        parent::__construct(_('Bitte bestätigen Sie, dass Sie kein Roboter sind'));
+
+        $captchaInput = new CaptchaInput('altcha', $this->legend, null);
+        $captchaInput->setStoringFunction(function (string $payload) {
+            $json = CaptchaChallenge::decodePayload($payload);
+
+            CaptchaChallenge::create([
+                'salt'   => $json['salt'],
+                'number' => $json['number'],
+            ]);
+        });
+        $this->addInput($captchaInput);
+    }
+}
diff --git a/lib/classes/forms/CaptchaInput.php b/lib/classes/forms/CaptchaInput.php
new file mode 100644
index 0000000..6476f87
--- /dev/null
+++ b/lib/classes/forms/CaptchaInput.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace Studip\Forms;
+
+use CaptchaChallenge;
+use URLHelper;
+
+/**
+ * The Text class represents a part of a form that displays a captcha.
+ */
+final class CaptchaInput extends Input
+{
+    public function hasValidation(): bool
+    {
+        return true;
+    }
+
+    public function getValidationCallback(): callable
+    {
+        return fn($value) => \CaptchaChallenge::validatePayload($value);
+    }
+
+    public function render(): string
+    {
+        return sprintf(
+            '<captcha-input challenge-url="%s" v-model="%s" auto="onload"></captcha-input>',
+            URLHelper::getLink('dispatch.php/captcha/challenge', [], true),
+            htmlReady($this->name)
+        );
+    }
+
+    public function renderWithCondition(): string
+    {
+        return $this->render();
+    }
+
+
+}
diff --git a/lib/classes/forms/Form.php b/lib/classes/forms/Form.php
index fa0422e..9c22c4f 100644
--- a/lib/classes/forms/Form.php
+++ b/lib/classes/forms/Form.php
@@ -297,6 +297,8 @@ class Form extends Part
                     \PageLayout::postSuccess($this->success_message);
                 }
                 page_close();
+                //This indicates that the form has been stored successfully.
+                echo "STUDIPFORM_STORE_SUCCESS";
                 die();
             }
         }
@@ -309,7 +311,7 @@ class Form extends Part
             //verify the user input:
             $output = [];
             foreach ($this->getAllInputs() as $input) {
-                if ($input->validate) {
+                if ($input->hasValidation()) {
                     $callback = $input->getValidationCallback();
                     $value = $this->getStorableValueFromRequest($input);
                     $valid = $callback($value, $input);
@@ -317,7 +319,7 @@ class Form extends Part
                         $output[$input->getName()] = [
                             'name' => $input->getName(),
                             'label' => $input->getTitle(),
-                            'error' => $callback($value, $input)
+                            'error' => $valid,
                         ];
                     }
                 }
@@ -396,7 +398,7 @@ class Form extends Part
         $stored = 0;
 
         foreach ($this->getAllInputs() as $input) {
-            if ($input->validate) {
+            if ($input->hasValidation()) {
                 $callback = $input->getValidationCallback();
                 $value = $this->getStorableValueFromRequest($input);
                 $valid = $callback($value, $input);
@@ -450,7 +452,7 @@ class Form extends Part
 
     /**
      * Returns all the Part objects like Fieldsets as an array.
-     * @return array
+     * @return Part[]
      */
     public function getParts() : array
     {
@@ -492,7 +494,7 @@ class Form extends Part
     /**
      * Renders the whole form as a string.
      * @return string
-     * @throws \Flexi_TemplateNotFoundException
+     * @throws \Flexi\TemplateNotFoundException
      */
     public function render()
     {
diff --git a/lib/classes/forms/Input.php b/lib/classes/forms/Input.php
index 9d2ad32..ef506e9 100644
--- a/lib/classes/forms/Input.php
+++ b/lib/classes/forms/Input.php
@@ -150,12 +150,17 @@ abstract class Input
     }
 
     /**
-     * Returns the value of this input.
-     * @return null
+     * Returns the value of this input. If $this->value is a callable this->getValue() returns the computed result.
+     * @return mixed
      */
     public function getValue()
     {
-        return $this->value;
+        if (is_callable($this->value)) {
+            $callable = $this->value;
+            return $callable();
+        } else {
+            return $this->value;
+        }
     }
 
     /**
diff --git a/lib/classes/forms/Part.php b/lib/classes/forms/Part.php
index fdca8f5..779cab7 100644
--- a/lib/classes/forms/Part.php
+++ b/lib/classes/forms/Part.php
@@ -139,7 +139,7 @@ abstract class Part
 
     /**
      * Recursively returns all Input elements attached to this Part object or any child Parts.
-     * @return array
+     * @return Input[]
      */
     public function getAllInputs()
     {
diff --git a/lib/classes/globalsearch/GlobalSearchCourses.php b/lib/classes/globalsearch/GlobalSearchCourses.php
index bf29ca0..9de5535 100644
--- a/lib/classes/globalsearch/GlobalSearchCourses.php
+++ b/lib/classes/globalsearch/GlobalSearchCourses.php
@@ -225,9 +225,9 @@ class GlobalSearchCourses extends GlobalSearchModule implements GlobalSearchFull
                     array_map(
                         function ($lecturer, $index) use ($search, $course) {
                             if ($index < 3) {
-                                return '<a href="' . URLHelper::getURL('dispatch.php/profile', ['username' => $lecturer->username]) . '">' . self::mark($lecturer->getUserFullname(), $search) . '</a>';
+                                return self::mark($lecturer->getUserFullname(), $search);
                             } else if ($index == 3) {
-                                return '<a href="' . URLHelper::getURL('dispatch.php/course/details/index/' . $course->id) . '">... (' . _('mehr') . ') </a>';
+                                return '... (' . _('mehr') . ')';
                             }
                         },
                         $lecturers,
diff --git a/lib/classes/globalsearch/GlobalSearchCourseware.php b/lib/classes/globalsearch/GlobalSearchCourseware.php
index d4c53b1..de069fe 100644
--- a/lib/classes/globalsearch/GlobalSearchCourseware.php
+++ b/lib/classes/globalsearch/GlobalSearchCourseware.php
@@ -142,7 +142,7 @@ class GlobalSearchCourseware extends GlobalSearchModule implements GlobalSearchF
                 'description' => $description,
                 'url' => $pageData['url'],
                 'img' => $structural_element->image ? $structural_element->getImageUrl() : Icon::create('courseware')->asImagePath(),
-                'additional' => '<a href="' . htmlReady($pageData['originUrl']) . '" title="' . htmlReady($pageData['originName']) . '">' . htmlReady($pageData['originName']) . '</a>',
+                'additional' => htmlReady($pageData['originName']),
                 'date' => $date->format('d.m.Y H:i'),
                 'structural-element-id' => $structural_element->id,
                 'expand' => null
diff --git a/lib/classes/globalsearch/GlobalSearchMessages.php b/lib/classes/globalsearch/GlobalSearchMessages.php
index d1a91a5..5f64b40 100644
--- a/lib/classes/globalsearch/GlobalSearchMessages.php
+++ b/lib/classes/globalsearch/GlobalSearchMessages.php
@@ -79,11 +79,7 @@ class GlobalSearchMessages extends GlobalSearchModule
 
             if ($user) {
                 $username = $user->getFullName();
-                $additional = sprintf(
-                    '<a href="%s">%s</a>',
-                    URLHelper::getLink('dispatch.php/profile', ['username' => $user->username]),
-                    self::mark($user->getFullName(), $search)
-                );
+                $additional = self::mark($user->getFullName(), $search);
             }
         }
 
diff --git a/lib/classes/globalsearch/GlobalSearchMyCourses.php b/lib/classes/globalsearch/GlobalSearchMyCourses.php
index f8f2f11..6558f78 100644
--- a/lib/classes/globalsearch/GlobalSearchMyCourses.php
+++ b/lib/classes/globalsearch/GlobalSearchMyCourses.php
@@ -162,9 +162,9 @@ class GlobalSearchMyCourses extends GlobalSearchModule
                     array_map(
                         function ($lecturer, $index) use ($search, $course) {
                             if ($index < 3) {
-                                return '<a href="' . URLHelper::getURL('dispatch.php/profile', ['username' => $lecturer->username]) . '">' . self::mark($lecturer->getUserFullname(), $search) . '</a>';
+                                return self::mark($lecturer->getUserFullname(), $search);
                             } else if ($index == 3) {
-                                return '<a href="' . URLHelper::getURL('dispatch.php/course/details/index/' . $course->id) . '">... (' . _('mehr') . ') </a>';
+                                return '... (' . _('mehr') . ')';
                             }
                         },
                         $lecturers,
diff --git a/lib/classes/globalsearch/GlobalSearchUsers.php b/lib/classes/globalsearch/GlobalSearchUsers.php
index fb8677a..458f098 100644
--- a/lib/classes/globalsearch/GlobalSearchUsers.php
+++ b/lib/classes/globalsearch/GlobalSearchUsers.php
@@ -86,7 +86,7 @@ class GlobalSearchUsers extends GlobalSearchModule implements GlobalSearchFullte
                 ['username' => $user->username],
                 true
             ),
-            'additional' => '<a href="' . URLHelper::getLink('dispatch.php/profile', ['username' => $user->username]) . '">' . self::mark($user->username, $search) . '</a>',
+            'additional' => self::mark($user->username, $search),
             'expand'     => self::getSearchURL($search),
             'img'        => Avatar::getAvatar($user->id)->getUrl(Avatar::MEDIUM),
         ];
diff --git a/lib/classes/helpbar/Helpbar.php b/lib/classes/helpbar/Helpbar.php
index cfa98a3..c4abfc4 100644
--- a/lib/classes/helpbar/Helpbar.php
+++ b/lib/classes/helpbar/Helpbar.php
@@ -253,7 +253,8 @@ class Helpbar extends WidgetContainer
         // add wiki link and remove it from navigation
         $this->addLink(
             _('Weiterführende Hilfe'),
-            format_help_url(PageLayout::getHelpKeyword()), Icon::create('link-extern', 'info_alt'),
+            PageLayout::getHelpUrl(),
+            Icon::create('link-extern', Icon::ROLE_INFO_ALT),
             '_blank',
             ['rel' => 'noopener noreferrer']
         );
@@ -264,7 +265,7 @@ class Helpbar extends WidgetContainer
             $template = $GLOBALS['template_factory']->open('helpbar/helpbar');
             $template->widgets   = $this->widgets;
             $template->open      = $this->open;
-            $template->tour_data = $tour_data;
+            $template->tour_data = $tour_data ?? null;
             $content = $template->render();
         }
 
diff --git a/lib/classes/librarysearch/LibraryDocument.class.php b/lib/classes/librarysearch/LibraryDocument.php
index 4c90e0b4..c1d297e 100644
--- a/lib/classes/librarysearch/LibraryDocument.class.php
+++ b/lib/classes/librarysearch/LibraryDocument.php
@@ -14,7 +14,6 @@
  * @since       4.6
  */
 
-
 /**
  * This class represents a document from a library.
  */
@@ -322,8 +321,8 @@ class LibraryDocument
         $doc->csl_data = $data['csl_data'];
         $doc->datafields = $data['datafields'];
         $doc->search_params = $data['search_params'];
-        $doc->catalog = $data['catalog'];
-        $doc->opac_link = $data['opac_link'];
+        $doc->catalog = $data['catalog'] ?? null;
+        $doc->opac_link = $data['opac_link'] ?? null;
         return $doc;
     }
 
@@ -386,12 +385,12 @@ class LibraryDocument
 
 
     /**
-     * @returns Flexi_Template A template containing information about the
+     * @returns Flexi\Template A template containing information about the
      *     the document.
      */
     public function getInfoTemplate($format = 'short')
     {
-        $factory = new Flexi_TemplateFactory(
+        $factory = new Flexi\Factory(
             $GLOBALS['STUDIP_BASE_PATH'] . '/templates/library/'
         );
         $template = $factory->open('library_document_info');
diff --git a/lib/classes/librarysearch/LibraryResultParser.interface.php b/lib/classes/librarysearch/LibraryResultParser.php
index eae45a4..eae45a4 100644
--- a/lib/classes/librarysearch/LibraryResultParser.interface.php
+++ b/lib/classes/librarysearch/LibraryResultParser.php
diff --git a/lib/classes/librarysearch/LibrarySearch.class.php b/lib/classes/librarysearch/LibrarySearch.php
index 473eacf..473eacf 100644
--- a/lib/classes/librarysearch/LibrarySearch.class.php
+++ b/lib/classes/librarysearch/LibrarySearch.php
diff --git a/lib/classes/librarysearch/LibrarySearchManager.class.php b/lib/classes/librarysearch/LibrarySearchManager.php
index ee9dc75..ee9dc75 100644
--- a/lib/classes/librarysearch/LibrarySearchManager.class.php
+++ b/lib/classes/librarysearch/LibrarySearchManager.php
diff --git a/lib/classes/librarysearch/resultparsers/BASELibraryResultParser.class.php b/lib/classes/librarysearch/resultparsers/BASELibraryResultParser.php
index b92628f..b92628f 100644
--- a/lib/classes/librarysearch/resultparsers/BASELibraryResultParser.class.php
+++ b/lib/classes/librarysearch/resultparsers/BASELibraryResultParser.php
diff --git a/lib/classes/librarysearch/resultparsers/K10PlusLibraryResultParser.class.php b/lib/classes/librarysearch/resultparsers/K10PlusLibraryResultParser.php
index b4b3a20..b4b3a20 100644
--- a/lib/classes/librarysearch/resultparsers/K10PlusLibraryResultParser.class.php
+++ b/lib/classes/librarysearch/resultparsers/K10PlusLibraryResultParser.php
diff --git a/lib/classes/librarysearch/resultparsers/MarcxmlLibraryResultParser.class.php b/lib/classes/librarysearch/resultparsers/MarcxmlLibraryResultParser.php
index 8017f3d..8017f3d 100644
--- a/lib/classes/librarysearch/resultparsers/MarcxmlLibraryResultParser.class.php
+++ b/lib/classes/librarysearch/resultparsers/MarcxmlLibraryResultParser.php
diff --git a/lib/classes/librarysearch/resultparsers/SRULibraryResultParser.class.php b/lib/classes/librarysearch/resultparsers/SRULibraryResultParser.php
index fed92f3..fed92f3 100644
--- a/lib/classes/librarysearch/resultparsers/SRULibraryResultParser.class.php
+++ b/lib/classes/librarysearch/resultparsers/SRULibraryResultParser.php
diff --git a/lib/classes/librarysearch/searchmodules/BASELibrarySearch.class.php b/lib/classes/librarysearch/searchmodules/BASELibrarySearch.php
index e0408e7..e0408e7 100644
--- a/lib/classes/librarysearch/searchmodules/BASELibrarySearch.class.php
+++ b/lib/classes/librarysearch/searchmodules/BASELibrarySearch.php
diff --git a/lib/classes/librarysearch/searchmodules/K10PlusZentralLibrarySearch.class.php b/lib/classes/librarysearch/searchmodules/K10PlusZentralLibrarySearch.php
index 9660cb4..9660cb4 100644
--- a/lib/classes/librarysearch/searchmodules/K10PlusZentralLibrarySearch.class.php
+++ b/lib/classes/librarysearch/searchmodules/K10PlusZentralLibrarySearch.php
diff --git a/lib/classes/librarysearch/searchmodules/SRULibrarySearch.class.php b/lib/classes/librarysearch/searchmodules/SRULibrarySearch.php
index b94869a..b94869a 100644
--- a/lib/classes/librarysearch/searchmodules/SRULibrarySearch.class.php
+++ b/lib/classes/librarysearch/searchmodules/SRULibrarySearch.php
diff --git a/lib/classes/restapi/ConsumerPermissions.php b/lib/classes/restapi/ConsumerPermissions.php
deleted file mode 100644
index 8fc2252..0000000
--- a/lib/classes/restapi/ConsumerPermissions.php
+++ /dev/null
@@ -1,212 +0,0 @@
-<?php
-namespace RESTAPI;
-use DBManager, PDO;
-
-/**
- * REST API routing permissions
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class ConsumerPermissions
-{
-    /**
-     * Create a permission object (for a certain consumer).
-     * Permissions object will be cached for each consumer.
-     *
-     * @param mixed $consumer_id Id of consumer (optional, defaults to global)
-     * @return ConsumerPermissions Returns permissions object
-     */
-    public static function get($consumer_id = null)
-    {
-        static $cache = [];
-        if (!isset($cache[$consumer_id])) {
-            $cache[$consumer_id] = new self($consumer_id);
-        }
-
-        return $cache[$consumer_id];
-    }
-
-    private $consumer_id;
-    private $permissions = [];
-
-    /**
-     * Creates the actual permission object (for a certain consumer).
-     *
-     * @param mixed $consumer_id Id of consumer (optional, defaults to global)
-     */
-    private function __construct($consumer_id = null)
-    {
-        $this->consumer_id = $consumer_id;
-
-        // Init with global permissions
-        $this->loadPermissions('global', true);
-
-        // Specific consumers permissions?
-        if ($consumer_id) {
-            $this->loadPermissions($consumer_id, false);
-        }
-    }
-
-    /**
-     * Defines whether access if allowed for the current consumer to the
-     * passed route via the passed method.
-     *
-     * @param String $route_id Route template (hash)
-     * @param String $method   HTTP method
-     * @param mixed  $granted  Granted state (PHP'ish boolean)
-     * @param bool   $overwrite May values be overwritten
-     * @return bool Indicates if value could be changed.
-     */
-    public function set($route_id, $method, $granted, $overwrite = false)
-    {
-        // If route_id is not an md5 hash, convert it
-        if (!preg_match('/^[0-9a-f]{32}$/', $route_id)) {
-            $route_id = md5($route_id);
-        }
-
-        if (!isset($this->permissions[$route_id])) {
-            // Skip if not globally set and not allowed to overwrite
-            if (!$overwrite) {
-                return false;
-            }
-            $this->permissions[$route_id] = [];
-        }
-
-        // overwrite only if globally allowed
-        if (!$overwrite && empty($this->permissions[$route_id][$method])) {
-            return false;
-        }
-
-        $this->permissions[$route_id][$method] = (bool) $granted;
-
-        return true;
-    }
-
-    /**
-     * Convenience method for activating all routes in a route map.
-     *
-     * @param  \RESTAPI\RouteMap $routemap RouteMap to activate
-     */
-    public function activateRouteMap(RouteMap $routemap)
-    {
-        foreach ($routemap->getRoutes() as $method => $routes) {
-            foreach (array_keys($routes) as $route) {
-                $this->set($route, $method, true, true);
-            }
-        }
-
-        $this->store();
-    }
-
-    /**
-     * Removes stored permissions for a given route and method.
-     *
-     * @param String $route_id Route template
-     * @param String $method HTTP method
-     * @return bool
-     */
-    public function remove($route_id, $method)
-    {
-        if (!isset($this->permissions[$route_id][$method])) {
-            return false;
-        }
-
-        unset($this->permissions[$route_id][$method]);
-
-        if (count($this->permissions[$route_id]) === 0) {
-            unset($this->permissions[$route_id]);
-        }
-
-        return true;
-    }
-
-    /**
-     * Convenience method for deactivating all routes in a route map.
-     *
-     * @param \RESTAPI\RouteMap $routemap RouteMap to activate
-     */
-    public function deactivateRouteMap(RouteMap $routemap)
-    {
-        foreach ($routemap->getRoutes() as $method => $routes) {
-            foreach (array_keys($routes) as $route) {
-                $this->remove($route, $method);
-            }
-        }
-
-        $this->store();
-    }
-
-    /**
-     * Loads permissions for passed consumer.
-     *
-     * @param String $consumer_id Id of the consumer in question
-     * @param bool   $overwrite May values be overwritten
-     * @return ConsumerPermissions Returns instance of self to allow chaining
-     */
-    protected function loadPermissions($consumer_id, $overwrite = false)
-    {
-        $query = "SELECT route_id, method, granted
-                  FROM api_consumer_permissions
-                  WHERE consumer_id = IFNULL(:consumer_id, 'global')";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':consumer_id', $consumer_id);
-        $statement->execute();
-        $permissions = $statement->fetchAll(PDO::FETCH_ASSOC);
-
-        // Init with global permissions
-        foreach ($permissions as $permission) {
-            extract($permission);
-
-            $this->set($route_id, $method, $granted, $overwrite);
-        }
-
-        return $this;
-    }
-
-    /**
-     * Checks if access to passed route via passed method is allowed for
-     * the current consumer.
-     *
-     * @param String $route  Route template
-     * @param String $method HTTP method
-     * @return bool Indicates whether access is allowed
-     */
-    public function check($route, $method)
-    {
-        $route_id = md5($route);
-
-        return isset($this->permissions[$route_id][$method])
-            && $this->permissions[$route_id][$method];
-    }
-
-    /**
-     * Stores the set permissions.
-     *
-     * @return bool Returns true if permissions were stored successfully
-     */
-    public function store()
-    {
-        $result = true;
-
-        $query = "INSERT INTO api_consumer_permissions (route_id, consumer_id, method, granted)
-                  VALUES (:route, IFNULL(:consumer_id, 'global'), :method, :granted)
-                  ON DUPLICATE KEY UPDATE granted = VALUES(granted)";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':consumer_id', $this->consumer_id);
-
-        foreach ($this->permissions as $route_id => $methods) {
-            $statement->bindParam(':route', $route_id);
-            foreach ($methods as $method => $granted) {
-                $statement->bindParam(':method', $method);
-                $granted = (int) !empty($granted);
-                $statement->bindParam(':granted', $granted);
-                $result = $result && $statement->execute();
-            }
-        }
-
-        return $result;
-    }
-}
diff --git a/lib/classes/restapi/Response.php b/lib/classes/restapi/Response.php
deleted file mode 100644
index 4417979..0000000
--- a/lib/classes/restapi/Response.php
+++ /dev/null
@@ -1,164 +0,0 @@
-<?php
-namespace RESTAPI;
-
-/**
- * Response class for the rest api
- *
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class Response implements \ArrayAccess
-{
-    public $body, $status, $headers;
-
-    /**
-     * Constructor, sets vital information if provided.
-     *
-     * @param String $body    Body contents of the response, optional,
-     *                        defaults to empty string
-     * @param int    $status  HTTP status code, optional, defaults to 200
-     * @param Array  $headers HTTP headers, optional, defaults to no headers
-     */
-    public function __construct($body = '', $status = 200, $headers = [])
-    {
-        $this->body = $body;
-        $this->status = (int) $status;
-        $this->headers = (array) $headers;
-    }
-
-    /**
-     * Detects whether the response status is of success type (HTTP status 2xx)
-     *
-     * @return bool True if status is of success type, false otherwise
-     */
-    public function isSuccess()
-    {
-        return 200 <= $this->status && $this->status <= 299;
-    }
-
-    /**
-     * Finishes the response with the given response renderer.
-     *
-     * @param Renderer\DefaultRenderer $content_renderer Used response renderer,
-     *                                                   only applied if body is
-     *                                                   not a callable closure
-     */
-    public function finish($content_renderer)
-    {
-        if (!is_callable($this->body)) {
-            $content_renderer->render($this);
-        }
-    }
-
-    /**
-     * Sends the response.
-     */
-    public function output()
-    {
-        if (isset($this->status)) {
-            if (mb_strpos(PHP_SAPI, 'cgi') === 0) {
-                $this->sendHeader(sprintf('Status: %d %s', $this->status, $this->reason()));
-            } else {
-                $this->sendHeader(sprintf('HTTP/1.1 %d %s', $this->status, $this->reason()));
-            }
-        }
-
-        foreach ($this->headers as $k => $v) {
-            $this->sendHeader("$k: $v", false, $this->status);
-        }
-
-        if (is_callable($this->body)) {
-            call_user_func($this->body);
-        } else {
-            echo $this->body;
-        }
-    }
-
-    /**
-     * Internally used function to actually send headers
-     *
-     * @param  string     the HTTP header
-     * @param  bool       optional; TRUE if previously sent header should be
-     *                    replaced - FALSE otherwise (default)
-     * @param  integer    optional; the HTTP response code
-     *
-     * @return void
-     */
-    public function sendHeader($header, $replace = FALSE, $status = NULL) {
-        if (isset($status)) {
-            header($header, $replace, $status);
-        }
-        else {
-            header($header, $replace);
-        }
-    }
-
-    /**
-     * Returns the reason phrase of this response according to RFC2616.
-     *
-     * @return string  the reason phrase for this response's status
-     */
-    public function reason() {
-        $reason = [
-            100 => 'Continue', 'Switching Protocols',
-            200 => 'OK', 'Created', 'Accepted', 'Non-Authoritative Information',
-                   'No Content', 'Reset Content', 'Partial Content',
-            300 => 'Multiple Choices', 'Moved Permanently', 'Found', 'See Other',
-                   'Not Modified', 'Use Proxy', '(Unused)', 'Temporary Redirect',
-            400 => 'Bad Request', 'Unauthorized', 'Payment Required','Forbidden',
-                   'Not Found', 'Method Not Allowed', 'Not Acceptable',
-                   'Proxy Authentication Required', 'Request Timeout', 'Conflict',
-                   'Gone', 'Length Required', 'Precondition Failed',
-                   'Request Entity Too Large', 'Request-URI Too Long',
-                   'Unsupported Media Type', 'Requested Range Not Satisfiable',
-                   'Expectation Failed',
-            500 => 'Internal Server Error', 'Not Implemented', 'Bad Gateway',
-                   'Service Unavailable', 'Gateway Timeout',
-                   'HTTP Version Not Supported'];
-
-        return isset($reason[$this->status]) ? $reason[$this->status] : '';
-    }
-
-    // array access methods for headers
-
-    /**
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
-    {
-        return isset($this->headers[$offset]);
-    }
-
-    /**
-     * @param $offset
-     * @return mixed
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
-     */
-    #[\ReturnTypeWillChange]
-    public function offsetGet($offset)
-    {
-        return @$this->headers[$offset];
-    }
-
-    /**
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
-    {
-        $this->headers[$offset] = $value;
-    }
-
-    /**
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($offset)
-    {
-        unset($this->headers[$offset]);
-    }
-}
diff --git a/lib/classes/restapi/RouteMap.php b/lib/classes/restapi/RouteMap.php
deleted file mode 100644
index b8ad2f4..0000000
--- a/lib/classes/restapi/RouteMap.php
+++ /dev/null
@@ -1,1060 +0,0 @@
-<?php
-namespace RESTAPI;
-
-use Config;
-use Request;
-use gossi\docblock\Docblock;
-
-/**
- * RouteMaps define and group routes to resources.
- *
- * Instances of RouteMaps are registered with the RESTAPI\Router to
- * participate in the routing business.
- *
- * A RouteMap defines at least one handler method which has to be
- * annotated with one of these annotations correlating to HTTP request
- * methods:
- *
- * @code
- * / * *
- *  * An example handler method
- *  *
- *  * @get /foo
- *  * @post /bar/:id
- *  * @put /baz/:id/:other_id
- *  * @delete /
- *  * /
- *  public function anyMethodName($id, $other_id = null) {}
- * @endcode
- *
- * By default, all API routes are unaccessible for nobody users.
- * To explicitly allow access for nobody users, add the allow_nobody
- * tag to the handler method's doc block. Example:
- *
- * @code
- * / * *
- *  * Another example handler method
- *  *
- *  * @get /foo
- *  *
- *  * @allow_nobody
- *  * /
- * @endcode
- *
- * As soon as the Router matches a HTTP request to a handler defined
- * in a RouteMap, it calls RouteMap::init to initialize it and
- * especially the instance field `$this->response` of type
- * RESTAPI\Response. You do not call RouteMap::init on your own.
- *
- * After the router has initialized this RouteMap, the router tries to
- * call a method `before` of this signature:
- *
- * @code
- * public function before(Router $router, Array $handler, Array $parameters);
- * @endcode
- *
- * The parameter `$handler` is a callable (as in function is_callable)
- * consisting of the instance of this RouteMap and the name of a
- * method of this instance. You may change the values of this array to
- * redirect to another handler.
- *
- * The parameter `$parameters` is an associative array whose keys
- * correlate to the placeholders in the matched URI template. The
- * values are the actual values of that placeholders in regard to the
- * HTTP request.
- *
- *
- * After calling RouteMap::before control is transfered to the actual
- * handler method. The values of the placeholders in the URI template
- * of the annotation are send as arguments to the handler.
- *
- * Example: We have got this handler method defined:
- *
- * @code
- * / * *
- *  * @get /foo/:id/bar/:other_id
- *  * /
- * public function fooHandler($id, $other_id) {
- * }
- * @endcode
- *
- * The router receives a request like this: `http://[..]/foo/1/bar/2`
- * and matches it to our `fooHandler` which is then called something
- * like that:
- *
- * @code
- * $result = $routeMap->fooHandler(1, 2);
- * @endcode
- *
- * In your handler methods you have to process the input and return
- * some output data, which is then rendered in an appropriate way
- * after negotiating the content format in the Router.
- *
- * Thus the return value of your handler method becomes the body of
- * the HTTP response.
- *
- *
- * The RouteMap class defines several methods to ease up your work
- * with the HTTP specifica.
- *
- * The methods RouteMap::status, RouteMap::headers and RouteMap::body
- * correlate to the components of a HTTP response.
- *
- * There are helpers for returning paginated collections, see
- * RouteMap::paginated.
- *
- * If you encounter an error or have to stop further processing, see
- * methods RouteMap::halt, RouteMap::error and RouteMap::notFound.
- *
- * These methods are \a DISRUPTIVE as they immediately stop the control
- * flow in your handler:
- *
- * @code
- * public function fooHandler($id)
- * {
- *   // do something
- *
- *   $this->halt();
- *
- *   // this line will never be reached
- * }
- * @endcode
- *
- * If you want to simply send a redirection response (HTTP status code
- * of 302 or 303), you may find calling RouteMap::redirect helpful.
- *
- * To generate a URL to a handler, use RouteMap::url
- *
- * When you find the need to return the content of a file, please see
- * RouteMap::sendFile which will help you with streaming it to the
- * client. For custom streaming just return a Closure from your
- * handler method.
- *
- * There are several other methods which you may find useful each
- * matching a HTTP header:
- *
- *   - RouteMap::contentType
- *   - RouteMap::etag
- *   - RouteMap::expires
- *   - RouteMap::cacheControl
- *   - RouteMap::lastModified
- *
- * You can access the data sent in the body of the current HTTP
- * request using the `$this->data` instance variable.
- *
- *   - If the request was of Content-Type `application/json`, the
- *     body of the request is decoded using `json_decode`.
- *   - If the request was of Content-Type
- *     `application/x-www-form-urlencoded`, the body of the request is
- *     decoded using `parse_str`.
- *   - Otherwise the request will not be parsed and `$this->data` will
- *     just contain the raw string.
- *
- * NOTE: The result of the described parsing will always contain
- *       strings encoded in windows-1252. If the original body
- *       was UTF-8 encoded, it is automatically re-encoded to windows-1252.
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-abstract class RouteMap
-{
-    protected $router;
-    protected $route;
-    protected $data = null;
-    protected $response;
-
-    /**
-     * Internal property which is used by RouteMap::paginated and
-     * contains everything about a paginated collection.
-     */
-    protected $pagination = false;
-
-    /**
-     * The offset into a RouteMap::paginated collection as requested
-     * by the client.
-     */
-    protected $offset;
-
-    /**
-     * The limit of a RouteMap::paginated collection as requested
-     * by the client.
-     */
-    protected $limit;
-
-    /**
-     * Constructor of the route map. Initializes neccessary offset and limit
-     * parameters for pagination.
-     */
-    public function __construct()
-    {
-        $this->offset = Request::int('offset', 0);
-        $this->limit  = Request::int('limit', Config::get()->ENTRIES_PER_PAGE);
-    }
-
-    /**
-     * Initializes the route map by binding it to a router and passing in
-     * the current route.
-     *
-     * @param Router $router Router to bind this route map to
-     * @param array $route   The matched route out of Router::matchRoute;
-     *                       an array with keys 'handler', 'conditions' and
-     *                       'source'
-     */
-    public function init($router, $route)
-    {
-        $this->router   = $router;
-        $this->route    = $route;
-        $this->response = new Response();
-
-        if ($mediaType = $this->getRequestMediaType()) {
-            $this->data = $this->parseRequestBody($mediaType);
-        }
-    }
-
-    /**
-     * Marks this chunk of data as a slice of a larger data set with
-     * a sum of "total" entries.
-     *
-     * @param mixed $data         Chunk of data (should be sliced according
-     *                            to current offset and limit parameters).
-     * @param int   $total        The total number of data entries in the
-     *                            according set.
-     * @param array $uri_params   Neccessary parameters when generating uris
-     *                            for the current route.
-     * @param array $query_params Optional query parameters.
-     */
-    public function paginated($data, $total, $uri_params = [], $query_params = [])
-    {
-        $uri = $this->url($this->route['uri_template']->inject($uri_params), $query_params);
-
-        $this->paginate($uri, $total);
-        return $this->collect($data);
-    }
-
-
-    /**
-     * Low level method for paginating collections. You better use
-     * RouteMap::paginated instead of this.
-     *
-     * Set the pagination data used by the RouteMap::collect.
-     *
-     * @param String $uri_format
-     * @param int    $total
-     * @param mixed  $offset
-     * @param mixed  $limit
-     *
-     * @return Routemap Returns instance of self to allow chaining
-     */
-    public function paginate($uri_format, $total, $offset = null, $limit = null)
-    {
-        $total  = (int)$total;
-        $offset = (int)($offset ?: $this->offset ?: 0);
-        $limit  = (int)($limit ?: $this->limit);
-
-        $this->pagination = compact('uri_format', 'total', 'offset', 'limit');
-
-        return $this;
-    }
-
-    /**
-     * Low level method for paginating collections. You better use
-     * RouteMap::paginated instead of this.
-     *
-     * Adjusts the result set to return a collection. A collection consists
-     * of the passed data array and the associated pagination information
-     * if available.
-     *
-     * Be aware that the passed data has to be already sliced according to
-     * the pagination information.
-     *
-     * @param array $data Actual dataset
-     * @return array Collection "object"
-     */
-    public function collect($data)
-    {
-        $collection = [
-            'collection' => $data
-        ];
-        if (is_array($this->pagination)) {
-            extract($this->pagination);
-
-            $offset = $offset - $offset % $limit;
-            $max    = ($total % $limit)
-                    ? $total - $total % $limit
-                    : $total - $limit;
-
-            $pagination = compact('total', 'offset', 'limit');
-            if ($total > $limit) {
-                $links = [];
-
-                foreach ([
-                             'first' => 0,
-                             'previous' => max(0, $offset - $limit),
-                             'next' => min($max, $offset + $limit),
-                             'last' => $max]
-                         as $key => $offset)
-                {
-                    $links[$key] = \URLHelper::getURL($uri_format, compact('offset', 'limit'));
-                }
-
-                $pagination['links'] = $links;
-            }
-            $collection['pagination'] = $pagination;
-        }
-        return $collection;
-    }
-
-    /************************/
-    /* REQUEST BODY METHODS */
-    /************************/
-
-    // find the requested media type
-    private function getRequestMediaType()
-    {
-        if (!empty($_SERVER['CONTENT_TYPE'])) {
-            $contentTypeParts = preg_split('/\s*[;,]\s*/', $_SERVER['CONTENT_TYPE']);
-            return mb_strtolower($contentTypeParts[0]);
-        }
-    }
-
-    // media-types that we know how to process
-    private static $mediaTypes = [
-        'application/json' => 'parseJson',
-        'application/x-www-form-urlencoded' => 'parseFormEncoded',
-        'multipart/form-data' => 'parseMultipartFormdata'
-    ];
-
-    // cache the request body
-    private static $_request_body;
-
-    // reads the HTTP request body
-    private function parseRequestBody($mediaType)
-    {
-        // read it only once
-        if (!isset(self::$_request_body)) {
-            self::$_request_body = file_get_contents('php://input');
-        }
-
-        if (isset(self::$mediaTypes[$mediaType])) {
-            $result = call_user_func([__CLASS__, self::$mediaTypes[$mediaType]], self::$_request_body);
-            if ($result) {
-                return $result;
-            }
-        }
-        return self::$_request_body;
-    }
-
-    // strategy to decode JSON strings
-    private static function parseJson($input)
-    {
-        return json_decode($input, true);
-    }
-
-    // strategy to decode form encoded strings
-    private static function parseFormEncoded($input)
-    {
-        parse_str($input, $result);
-        return $result;
-    }
-
-    // strategy to decode a multipart message. Used for file-uploads.
-    private static function parseMultipartFormdata($input)
-    {
-
-        $data = [];
-        if (Request::isPost()) {
-            foreach ($_POST as $key => $value) {
-                $data[$key] = $value;
-            }
-            $data['_FILES'] = $_FILES;
-            return $data;
-        }
-        $boundary = self::getMultipartBoundary();
-        if (!$boundary) {
-            return $data;
-        }
-        $input = explode("--".$boundary, $input);
-
-        array_pop($input);
-        array_shift($input);
-
-        foreach ($input as $part) {
-            $part = ltrim($part, "\r\n");
-            [$head, $body] = explode("\r\n\r\n", $part, 2);
-
-            $tmpheaders = $headers = [];
-            foreach (explode("\r\n", $head) as $headline) {
-                if (preg_match('/^[^\s]/', $headline)) {
-                    $lineIsHeader = preg_match('/([^:]+):\s*(.*)$/', $headline, $matches);
-                    if ($lineIsHeader) {
-                        $tmpheaders[] = ['index' => mb_strtolower(trim($matches[1])), 'value' => trim($matches[2])];
-                    }
-                } else {
-                    //noch zur letzten Zeile hinzuzählen
-                    end($tmpheaders);
-                    $lastkey = key($tmpheaders);
-                    $tmpheaders[$lastkey]['value'] .= " ".mb_substr($headline, 1);
-                }
-            }
-            foreach ($tmpheaders as $header) {
-                $headers[$header['index']] = $header['value'];
-            }
-
-            $contentType = "";
-            if (isset($headers['content-type'])) {
-                preg_match("/^([^;\s]*)/", $headers['content-type'], $matches);
-                $contentType = mb_strtolower($matches[1]);
-            }
-            switch ($headers["transfer-encoding"]) {
-                case "quoted-printable":
-                    $body = quoted_printable_decode($body);
-                    break;
-                case "base64":
-                    $body = base64_decode(preg_replace("/(\r?\n|\r)/", "", trim($body)));
-                    break;
-                case "7bit":
-                case "8bit":
-                default:
-                    //nothing to do
-            }
-            $matches = [];
-            preg_match("/name=([^;\s]*)/i", $headers['content-disposition'], $matches);
-            $name = str_replace(["'", '"'], '', $matches[1]);
-            if (!$contentType) {
-                $data[$name] = mb_substr($body, 0, mb_strlen($body) - 2);
-            } else {
-                switch ($contentType) {
-                    case 'application/json':
-                        $data = array_merge($data, self::parseJson($body));
-                        break;
-                    case 'application/x-www-form-urlencoded':
-                        $data = array_merge($data, self::parseFormEncoded($body));
-                        break;
-                    default:
-                        $matches = [];
-                        preg_match("/filename=([^;\s]*)/i", $headers['content-disposition'], $matches);
-                        if (!$matches[1]) {
-                            preg_match('/filename=([^;\s]*)/i', $headers['content-type'], $matches);
-                        }
-                        $filename = str_replace(["'", '"'], '', $matches[1]);
-                        $tmp_name = $GLOBALS['TMP_PATH']."/uploadfile_".md5(uniqid());
-                        $handle = fopen($tmp_name, 'wb');
-                        $filesize = fwrite($handle, $body, (mb_strlen($body) - 2));
-                        fclose($handle);
-                        $data['_FILES'][$name] = [
-                            'name' => $filename,
-                            'type' => $contentType,
-                            'tmp_name' => $tmp_name,
-                            'size' => $filesize
-                        ];
-                }
-            }
-        }
-        return $data;
-    }
-
-    private static function getMultipartBoundary()
-    {
-        if ($contentType = $_SERVER['CONTENT_TYPE']) {
-            foreach (preg_split('/\s*[;,]\s*/', $contentType) as $part) {
-                if (mb_strtolower(mb_substr($part, 0, 8)) === "boundary") {
-                    $part = explode("=", $part);
-                    return $part[1];
-                }
-            }
-        }
-        return null;
-    }
-
-
-    /**
-     * Set the HTTP status of the current response.
-     *
-     * @param integer $status  the HTTP status of the response
-     */
-    public function status($status)
-    {
-        $this->response->status = $status;
-    }
-
-    /**
-     * Set multiple response headers of the current response by
-     * merging them with already set ones.
-     *
-     * @code
-     * $routemap->headers(array('X-example' => "yep"));
-     * @endcode
-     *
-     * @param array $headers  the headers to set
-     *
-     * @return array  the headers of the current response
-     */
-    public function headers($headers = [])
-    {
-        if (sizeof($headers)) {
-            $this->response->headers = array_merge($this->response->headers, $headers);
-        }
-        return $this->response->headers;
-    }
-
-    /**
-     * Set the HTTP body of the current response.
-     *
-     * @param string $body  the body to send back
-     */
-    public function body($body)
-    {
-        $this->response->body = $body;
-    }
-
-
-    /**
-     * Set the Content-Type of the HTTP response given a mime type and
-     * optionally further parameters as discusses in RFC 2616 14.17.
-     *
-     * If no charset is given, it defaults to Stud.IP's 'windows-1252'.
-     *
-     * Examples:
-     *
-     * @code
-     * // results in "Content-Type: image/gif"
-     * $this->contentType('image/gif);
-     *
-     * // results in "Content-Type: text/html;charset=ISO-8859-4"
-     * $this->contentType('text/html;charset=ISO-8859-4');
-     *
-     * // results in "Content-Type: text/html;charset=ISO-8859-4"
-     * $this->contentType('text/html', array('charset' => 'ISO-8859-4'));
-     *
-     * // results in "Content-type: multipart/byteranges; boundary=THIS_STRING_SEPARATES"
-     * $this->contentType('multipart/byteranges', array('boundary' => 'THIS_STRING_SEPARATES'));
-     *
-     * @endcode
-     *
-     * @param string $mime_type  a string describing a MIME type like 'application/json'
-     * @param array  $params     optional parameters as described above
-     */
-    public function contentType($mime_type, $params = [])
-    {
-        if (!isset($params['charset'])) {
-            $params['charset'] = 'utf-8';
-        }
-
-        if (mb_strpos($mime_type, 'charset') !== FALSE) {
-            unset($params['charset']);
-        }
-
-        if (sizeof($params)) {
-            $mime_type .= mb_strpos($mime_type, ';') !== FALSE ? ', ' : ';';
-            $ps = [];
-            foreach ($params as $k => $v) {
-                $ps[] = $k . '=' . $v;
-            }
-            $mime_type .= join(', ', $ps);
-        }
-
-        $this->response['Content-Type'] = $mime_type;
-    }
-
-    /**
-     * (Nice) sugar for calling RouteMap::halt and therefore
-     * as \a DISRUPTIVE. Code after calling RouteMap::error will not
-     * be evaluated.
-     *
-     * @see RouteMap::halt
-     *
-     * @param integer $status  a number indicating the HTTP status
-     *                         code; probably something 4xx or 5xx-ish
-     * @param string $body     optional; the body of the HTTP response
-     *
-     */
-    public function error($status, $body = null)
-    {
-        $this->halt($status, [], $body);
-    }
-
-
-    /**
-     * Sets the HTTP response's Etag header and halts, if the incoming
-     * HTTP request was a matching conditional GET using an
-     * 'If-None-Match' header. Thus it is a possibly \a DISRUPTIVE
-     * method as it will stop evaluation in that case and send a '304
-     * Not Modified'.
-     *
-     * Detail: If the request contains an If-Match or If-None-Match
-     * header set to `*`, a RouteMap assumes a match on safe
-     * (e.g. GET) and idempotent (e.g. PUT) requests. (In those cases
-     * it thinks that the resource already exists and therefore
-     * matches a wildcard.). This can be changed by passing an
-     * appropriate value for the `$new_resource` parameter.
-
-     * Details of this can be found in RFC 2616 14.24 and 14.26
-     *
-     * @param string $value       an identifier uniquely identifying the
-     *                            current state of a resource
-     * @param bool $strong_etag   optional; indicates whether the etag
-     *                            is a weak or strong (which is the
-     *                            default) cache validator. Have a look
-     *                            at the RFC for details.
-     * @param bool $new_resource  optional; a way to tell the RouteMap
-     *                            that this is a new or existing
-     *                            resource. See above.
-     */
-
-    public function etag($value, $strong_etag = true, $new_resource = null)
-    {
-        // Before touching this code, please double check RFC 2616
-        // 14.24 and 14.26.
-
-        if (!isset($new_resource)) {
-            $new_resource = Request::isPost();
-        }
-
-        $value = '"' . $value . '"';
-        if (!$strong_etag) {
-            $value = 'W/' . $value;
-        }
-        $this->response['ETag'] = $value;
-
-        if ($this->response->isSuccess() || $this->response->status === 304) {
-            if (isset($_SERVER['HTTP_IF_NONE_MATCH']) && $this->etagMatches($_SERVER['HTTP_IF_NONE_MATCH'], $new_resource)) {
-                $this->halt($this->isRequestSafe() ? 304 : 412);
-            }
-            if (isset($_SERVER['HTTP_IF_MATCH'])
-                && !$this->etagMatches($_SERVER['HTTP_IF_MATCH'], $new_resource)) {
-                $this->halt(412);
-            }
-        }
-    }
-
-    // Helper method checking if a ETag value list includes the current ETag.
-    private function etagMatches($list, $new_resource)
-    {
-        if ($list === '*') {
-            return !$new_resource;
-        }
-
-        return in_array($this->response['ETag'],
-                        preg_split('/\s*,\s*/', $list));
-    }
-
-    // Helper method checking if the request is safe
-    private function isRequestSafe()
-    {
-        $method = Request::method();
-        return $method === 'GET' or $method === 'HEAD' or $method === 'OPTIONS' or $method === 'TRACE';
-    }
-
-    /**
-     * This sets the `Expires` header and the `Cache-Control`
-     * directive `max-age`.
-     *
-     * Amount is an integer number of seconds in the future indicating
-     * when the response should be considered "stale". The
-     * `$cache_control` parameter is passed to RouteMap#cacheControl
-     * along with the automatically generated `max_age` directive.
-     *
-     * @param int $amount  an integer specifying the number of seconds
-     *                     this resource will go stale.
-     * @param array $cache_control  optional; more directives for
-     *                     RouteMap::cacheControl which is always
-     *                     automatically called using the computed max_age
-     */
-    public function expires($amount, $cache_control = [])
-    {
-        $time = time() + $amount;
-        $max_age = $amount;
-
-        $cache_control[] = "max-age=$max_age";
-        $this->cacheControl($cache_control);
-
-        $this->response['Expires'] = $this->httpDate($time);
-    }
-
-    /**
-     * This sets the Cache-Control header of the HTTP response.
-     *
-     * Example:
-     *
-     * @code
-     * $this->cacheControl(array('public', 'must-revalidate'));
-     * @endcode
-     *
-     * @param array $values  an array containing Cache-Control
-     *                       directives.
-     */
-    public function cacheControl($values)
-    {
-        if (is_array($values) && sizeof($values)) {
-            $this->response['Cache-Control'] = join(', ', $values);
-        }
-    }
-
-    /**
-     * This very important method stops further execution of your
-     * code. You may specify a status code, headers and the body of
-     * the resulting response. As the name implies, this method is \a
-     * DISRUPTIVE and will not return.
-     *
-     * @code
-     * // stops any further code of a route
-     * $this->halt();
-     *
-     * // you may specify an HTTP status
-     * $this->halt(409):
-     *
-     * // you may specify the HTTP response's body
-     * $this->halt('my ethereal body')
-     *
-     * // or even both
-     * $this->halt(100, 'Yes, pleazze!')
-     *
-     * // giving headers
-     * $this->halt(417, array('Content-Type' => 'x-not-a-cat'), 'Cats only!')
-     * @endcode
-     *
-     * This method is called by every single \a DISRUPTIVE method.
-     *
-     * @param integer $status  optional; the response's status code
-     * @param array $headers   optional; (additional) header lines
-     *                           which get merged with already set headers
-     * @param string $body     optional; the response's body
-     */
-    public function halt(/* [status], [headers], [body] */)
-    {
-        $args   = func_get_args();
-        $result = [];
-
-        $constraints = [
-            'status'  => 'is_int',
-            'headers' => 'is_array',
-            'body'    => function ($i) { return isset($i); } // #existy
-        ];
-        foreach ($constraints as $state => $constraint) {
-            if ($constraint(current($args))) {
-                call_user_func([$this, $state], array_shift($args));
-            }
-        }
-
-        throw new RouterHalt($this->response);
-    }
-
-    /**
-     * This method sets the Last-Modified header of the HTTP response
-     * and halts on matching conditional GET requests. Thus this
-     * method is \a DISRUPTIVE in certain circumstances.
-     *
-     * You have to give an integer typed timestamp (in seconds since
-     * epoch) to specify the data of the last modification to the
-     * requested resource.
-     *
-     * If the current HTTP request contains an `If-Modified-Since`
-     * header, its value is compared to the specified `$time`
-     * parameter. Unless the header's value is sooner than the given
-     * `$time`, further execution is precluded and the RouteMap
-     * returns with a '304 Not Modified'.
-     *
-     * @param integer $time  a timestamp described in seconds since epoch
-     */
-    public function lastModified($time)
-    {
-
-        $this->response['Last-Modified'] = $this->httpDate($time);
-
-        if (isset($_SERVER['HTTP_IF_NONE_MATCH'])) {
-            return;
-        }
-
-        if ($this->response->status === 200
-            && isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {
-            // compare based on seconds since epoch
-            $since = $this->httpdate($_SERVER['HTTP_IF_MODIFIED_SINCE']);
-            if ($since >= (int) $time) {
-                $this->halt(304);
-            }
-        }
-
-        if (($this->response->isSuccess() || $this->response->status === 412)
-            && isset($_SERVER['HTTP_IF_UNMODIFIED_SINCE'])) {
-
-            // compare based on seconds since epoch
-            $since = $this->httpdate($_SERVER['HTTP_IF_UNMODIFIED_SINCE']);
-
-            if ($since < (int) $time) {
-                $this->halt(412);
-            }
-        }
-    }
-
-    private function httpDate($timestamp)
-    {
-        return gmdate('D, d M Y H:i:s \G\M\T', (int) $timestamp);
-    }
-
-    /**
-     * Halts execution and returns a '404 Not Found' response.
-     *
-     * Sugar for calling RouteMap::error(404) and therefore
-     * \a DISRUPTIVE. Code after calling RouteMap::notFound will
-     * not be evaluated.
-     *
-     * @see RouteMap::error
-     * @see RouteMap::halt
-     *
-     * @param string $body     optional; the body of the HTTP response
-     */
-    public function notFound($body = null)
-    {
-        $this->halt(404, $body);
-    }
-
-    /**
-     * Stops your code and redirects to the URL provided. This method
-     * is \a DISRUPTIVE like RouteMap#halt
-     *
-     * In addition to the URL you may provide the status code,
-     * (additional) headers and a request body as you would when
-     * calling RouteMap#halt.
-     *
-     * @code
-     * $this->redirect('/foo', 201, array('X-Some-Header' => 1234), 'and even a body');
-     * @endcode
-     *
-     * @see RouteMap::halt
-     *
-     * @param string $url the URL to redirect to; it will be filtered
-     *                    using RouteMap#url, so you may call it with
-     *                    those nice and small strings used in the
-     *                    annotations
-     * @param mixed $args optional; any combinations of the three
-     *                    parameters as in RouteMap::halt
-     */
-    public function redirect($url, $args = null)
-    {
-        $this->status($_SERVER["SERVER_PROTOCOL"] === 'HTTP/1.1' && !Request::isGet() ? 303 : 302);
-        $this->response['Location'] = $this->url($url);
-
-        $args = array_slice(func_get_args(), 1);
-        call_user_func_array([$this, 'halt'], $args);
-    }
-
-
-    /**
-     * Stops execution of your code and starts sending the specified
-     * file. This method is \a DISRUPTIVE.
-     *
-     * Using the `$opts` parameter you may specify the file's mime
-     * content type, sending an appropriate 'Content-Type' header, and
-     * you may specify the 'Content-Disposition' of the file transfer.
-     *
-     * Example:
-     *
-     * @code
-     * $this->sendFile('/tmp/c29tZSB0ZXh0', array(
-     *     'type' => 'image/png',
-     *     'disposition' => 'inline',
-     *     'filename' => 'cutecats.png'));
-     * @endcode
-     *
-     * @param string $_path  the filesystem path to the file to send
-     * @param array  $opts   optional; specify the content type,
-     *                       disposition and filename
-     */
-    public function sendFile($_path, $opts = [])
-    {
-        $path = realpath($_path);
-
-        if (!file_exists($path)) {
-            $this->notFound('File to send does not exist');
-        }
-
-        if (isset($opts['type'])) {
-            $this->contentType($opts['type']);
-        } else if (!isset($this->response['Content-Type'])) {
-            $this->contentType(get_mime_type($path));
-        }
-
-        if ($opts['disposition'] === 'attachment' || isset($opts['filename'])) {
-            $this->response['Content-Disposition'] = 'attachment; ';
-            $filename = $opts['filename'] ?: $path;
-            $this->response['Content-Disposition'] .= encode_header_parameter('filename', basename($filename));
-        }
-
-        elseif ($opts['disposition'] === 'inline') {
-            $this->response['Content-Disposition'] = 'inline';
-        }
-
-        // TODO add HTTP 'Range' support
-
-        $size = filesize($path);
-        $this->response['Content-Length'] = $size;
-
-        // End all potential output buffers
-        while (ob_get_level() > 0) {
-            ob_end_clean();
-        }
-
-        // Send file
-        $this->halt(200, $this->response->headers, function () use ($path) {
-            readfile($path);
-        });
-    }
-
-
-    /**
-     * Generate a URL to a given handler using a URL fragment and URL
-     * parameters.
-     *
-     * Example:
-     * @code
-     * // result in something like "/some/path/api.php/course/123/members?status=student"
-     * $this->url('course/123/members', array('status' => 'student'));
-     * @endcode
-     *
-     * @param string $addr       a URL fragment to a handler
-     * @param array $url_params  optional; URL parameters to add to
-     *                           the generated URL
-     *
-     * @return string  the resulting URL
-     */
-    public function url($addr, $url_params = null)
-    {
-        $addr = ltrim($addr, '/');
-        return \URLHelper::getURL("api.php/$addr", $url_params, true);
-    }
-
-    /**
-     * A `vsprintf` like variant to the RouteMap::url method.
-     *
-     * Example:
-     * @code
-     * // results in "[...]/api.php/foo/some_id?status=student"
-     * $this->urlf("foo/%s", array("some_id"), array('status' => 'student'));
-     * @endcode
-     *
-     * @param string $addr_f        a URL fragment to a handler
-     *                              containing sprintf-ish format sequences
-     * @param array $format_params  values to fill into the format markers
-     * @param array $url_params     optional; URL parameters to add to
-     *                              the generated URL
-     *
-     * @return string  the resulting URL
-     */
-
-    public function urlf($addr_f, $format_params, $url_params = null)
-    {
-        if (!is_array($format_params)) {
-            $format_params = [$format_params];
-        }
-        return $this->url(vsprintf($addr_f, $format_params), $url_params);
-    }
-
-    /**
-     * Returns a list of all the routes this routemap provides.
-     *
-     * @param string $http_method Return only the routes for this specific
-     *                            http method (optional)
-     *
-     * @return array of all routes grouped by method
-     */
-    public function getRoutes($http_method = null)
-    {
-        $ref      = new \ReflectionClass($this);
-
-        if ($ref->getDocComment()) {
-            $docblock = new Docblock($ref);
-            $class_conditions = $this->extractConditions($docblock);
-        } else {
-            $class_conditions = [];
-        }
-
-
-        // Create result array by creating an associative array from all
-        // supported methods as keys
-        $routes = array_fill_keys(Router::getSupportedMethods(), []);
-
-        // Restrict routes to given http method (if given)
-        if ($http_method !== null) {
-            $routes = [$http_method => []];
-        }
-
-        // Iterate through all methods of the routemap
-        foreach ($ref->getMethods( \ReflectionMethod::IS_PUBLIC) as $ref_method) {
-            // No docblock? Not an api route!
-            if (!$ref_method->getDocComment()) {
-                continue;
-            }
-
-            // Parse docblock
-            $docblock = new Docblock($ref_method);
-
-            // No docblock tags? Not an api route!
-            if ($docblock->getTags()->isEmpty()) {
-                continue;
-            }
-
-            // Any specific condition to consider?
-            $conditions = $this->extractConditions($docblock, $class_conditions);
-
-            // Iterate through all possible methods in order to identify
-            // any according docblock tags
-            $allow_nobody = $docblock->hasTag('allow_nobody');
-            foreach (array_keys($routes) as $http_method) {
-                if (!$docblock->hasTag($http_method)) {
-                    //The tag for the current HTTP method cannot be found
-                    //in the route's DocBlock tags.
-                    continue;
-                }
-
-                // Route all defined method and uri template combinations to
-                // the according methods of the object.
-                foreach ($docblock->getTags($http_method) as $tag) {
-                    $uri_template = trim($tag->getDescription());
-                    $routes[$http_method][$uri_template] = [
-                        'handler'      => [$this, $ref_method->name],
-                        'conditions'   => $conditions,
-                        'description'  => trim($docblock->getShortDescription()) ?: false,
-                        'allow_nobody' => $allow_nobody
-                    ];
-                }
-            }
-        }
-
-        // Return all routes grouped or just the routes for the wanted method
-        return func_num_args() === 1
-             ? reset($routes)
-             : $routes;
-    }
-
-    /**
-     * Extracts defined conditions from a given docblock.
-     *
-     * @param Docblock $docblock   DocBlock to examine
-     * @param array    $conditions Optional array of already defined
-     *                             conditions to extend
-     * @return array of all extracted conditions with the variable name
-     *         as key and pattern to match as value
-     */
-    protected function extractConditions($docblock, $conditions = [])
-    {
-        foreach ($docblock->getTags('condition') as $condition) {
-            [$var, $pattern] = explode(' ', $condition->getDescription(), 2);
-            $conditions[$var] = $pattern;
-        }
-
-        return $conditions;
-    }
-
-    /**
-     * Returns the response object
-     * @return Response
-     */
-    public function getResponse(): Response
-    {
-        return $this->response;
-    }
-}
diff --git a/lib/classes/restapi/Router.php b/lib/classes/restapi/Router.php
deleted file mode 100644
index df7a6b9..0000000
--- a/lib/classes/restapi/Router.php
+++ /dev/null
@@ -1,665 +0,0 @@
-<?php
-/** @namespace RESTAPI
- *
- * Im Namensraum RESTAPI sind alle Klassen und Funktionen versammelt,
- * die für die RESTful Web Services von Stud.IP benötigt werden.
- */
-namespace RESTAPI;
-use RESTAPI\Renderer\DefaultRenderer;
-
-/**
- * Die Aufgabe des Routers ist das Anlegen und Auswerten eines
- * Mappings von sogenannten Routen (Tupel aus HTTP-Methode und Pfad)
- * auf Code.
- *
- * Dazu werden zunächst Routen mittels der Funktion
- * Router::registerRoutes registriert.
- *
- * Wenn dann ein HTTP-Request eingeht, kann mithilfe von
- * Router::dispatch und HTTP-Methode bzw. Pfad der zugehörige Code
- * gefunden und ausgeführt werden. Der Router bildet aus dem
- * Rückgabewert des Codes ein Response-Objekt, das er als Ergebnis
- * zurück meldet.
- *
- * @code
- * $router = Router::getInstance();
- *
- * // register a sample Route
- * $router->registerRoutes(new ExampleRoute);
- *
- * // dispatch to therein defined Routes
- * $response = $router->dispatch('/example', 'GET');
- *
- * // render response
- * $response->output();
- *
- * @endcode
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @see        Inspired by http://blog.sosedoff.com/2009/07/04/simpe-php-url-routing-controller/
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class Router
-{
-    // instances are cached here
-    protected static $instances = [];
-
-    /**
-     * Holds the user object of the user that is accessing the API.
-     * This is null for nobody users.
-     */
-    protected $user = null;
-
-    /**
-     * Returns (and if neccessary, initializes) a (cached) router object for an
-     * optional consumer id.
-     *
-     * @param mixed $consumer_id ID of the consumer (defaults to 'global')
-     *
-     * @return Router returns the Router instance associated to the
-     *                consumer ID (or to the 'global' ID)
-     */
-    public static function getInstance($consumer_id = null)
-    {
-        $consumer_id = $consumer_id ?: 'global';
-
-        if (!isset(self::$instances[$consumer_id])) {
-            self::$instances[$consumer_id] = new self($consumer_id);
-        }
-        return self::$instances[$consumer_id];
-    }
-
-    // All supported method need to be defined here
-    protected static $supported_methods = [
-        'get', 'post', 'put', 'delete', 'patch', 'options', 'head'
-    ];
-
-    /**
-     * Returns a list of all supported methods.
-     *
-     * @return array of methods as strings
-     */
-    public static function getSupportedMethods()
-    {
-        return self::$supported_methods;
-    }
-
-    // registered routes by method and uri template
-    protected $routes = [];
-
-    // registered content renderers
-    protected $renderers = [];
-
-    // identified or forced content renderer
-    protected $content_renderer = false;
-
-    // default renderer
-    protected $default_renderer = false;
-
-    // registered conditions
-    protected $conditions = [];
-
-    // registered descriptions
-    protected $descriptions = [];
-
-    // registered consumers
-    protected $consumers = [];
-
-    // associated permissions
-    protected $permissions = false;
-
-    /**
-     * Constructs the router.
-     *
-     * @param mixed $consumer_id  the ID of the consumer this router
-     *                             should associate to
-     */
-    protected function __construct($consumer_id)
-    {
-        $this->permissions = ConsumerPermissions::get($consumer_id);
-        $this->registerRenderer(new Renderer\DefaultRenderer);
-    }
-
-    /**
-     * Registers a handler for a specific combination of request method
-     * and uri template.
-     *
-     * @param String  $request_method   expected HTTP request method
-     * @param String  $uri_template     expected URI template, for
-     *                                  example: \code "/user/:user_id/events" \endcode
-     * @param Array   $handler          request handler array:
-     *                                  \code array($object, "methodName") \endcode
-     * @param Array   $conditions       (optional) an associative
-     *                                  array using the name of
-     *                                  parameters as keys and regexps
-     *                                  as value
-     * @param string  $source           (optional) this denotes the
-     *                                  origin of a route. Usually
-     *                                  either 'core' or 'plugin', but
-     *                                  defaults to 'unknown'.
-     * @param bool    $allow_nobody     Whether the route can be accessed
-     *                                  as nobody user (true) or not (false).
-     *                                  Defaults to false.
-     *
-     * @return Router  returns itself to allow chaining
-     * @throws \Exception  if passed HTTP request method is not supported
-     */
-    public function register($request_method, $uri_template, $handler, $conditions = [], $source = 'unknown', $allow_nobody = false)
-    {
-        // Normalize method and test whether it's supported
-        $request_method = mb_strtolower($request_method);
-        if (!in_array($request_method, self::$supported_methods)) {
-            throw new \Exception('Method "' . $request_method . '" is not supported.');
-        }
-
-        // Initialize routes storage for this method if neccessary
-        if (!isset($this->routes[$request_method])) {
-            $this->routes[$request_method] = [];
-        }
-
-        // Normalize uri template (always starts with a slash)
-        if ($uri_template[0] !== '/') {
-            $uri_template = '/' . $uri_template;
-        }
-
-        // Sanitize conditions
-        foreach ($conditions as $var => $pattern) {
-            if ($pattern[0] !== $pattern[mb_strlen($pattern) - 1] || ctype_alnum($pattern[0])) {
-                $conditions[$var] = '/' . $pattern . '/';
-            }
-        }
-
-        $this->routes[$request_method][$uri_template] = compact(
-            'handler', 'conditions', 'source', 'allow_nobody'
-        );
-
-        // Return instance to allow chaining
-        return $this;
-    }
-
-    /**
-     * Registers the routes defined in a RouteMap instance using
-     * docblock annotations (like @get) of its methods.
-     *
-     * \code
-     * $router = \RESTAPI\Router::getInstance();
-     *
-     * $router->registerRoutes(new ExampleRouteMap());
-     * \endcode
-     *
-     * @param RouteMap $map  the RouteMap instance to register
-     *
-     * @return Router returns itself to allow chaining
-     */
-    public function registerRoutes(RouteMap $map)
-    {
-        // Investigate object, define whether it's located in the core system
-        // or a plugin, respect any defined class conditions and iterate
-        // through it's methods to find any defined route
-        $ref      = new \ReflectionClass($map);
-        $filename = $ref->getFilename();
-        $source   = mb_strpos($filename, 'plugins_packages') !== false
-                  ? 'plugin'
-                  : 'core';
-
-        foreach (self::$supported_methods as $http_method) {
-            foreach ($map->getRoutes($http_method) as $uri_template => $data) {
-                // Register (and describe) route
-                $this->register(
-                    $http_method, $uri_template,
-                    $data['handler'], $data['conditions'],
-                    $source,
-                    $data['allow_nobody']
-                );
-                if ($data['description']) {
-                    $this->describe(
-                        $uri_template,
-                        $data['description'],
-                        $http_method
-                    );
-                }
-            }
-        }
-
-        return $this;
-    }
-
-    /**
-     * Describe one or more routes.
-     *
-     * \code
-     * $router = \RESTAPI\Router::getInstance();
-     *
-     * // describe a single route
-     * $router->describe('/foo', 'returns everything about foo', 'get');
-     *
-     * // describe several routes that use the same path
-     * $router->describe('/foo', array(
-     *     'get'    => 'returns everything about foo',
-     *     'put'    => 'updates all of foo',
-     *     'delete' => 'empty up foo'
-     * ));
-     *
-     * // describe several routes
-     * $router->describe(array(
-     *     '/foo' => array(
-     *                   'get'    => 'returns everything about foo',
-     *                   'put'    => 'updates all of foo',
-     *                   'delete' => 'empty up foo'),
-     *     '/bar' => array(...),
-     * ));
-     * \endcode
-     *
-     * @param String|Array $uri_template  URI template to describe or pass an
-     *                                    array to describe multiple routes.
-     * @param String|null  $description   description of the route
-     * @param String       $method        method to describe.
-     *
-     * @return Router  returns instance of itself to allow chaining
-     */
-    public function describe($uri_template, $description = null, $method = 'get')
-    {
-        // describe multiple routes at once
-        if (func_num_args() === 1 && is_array($uri_template)) {
-            foreach ($uri_template as $template => $description) {
-                $this->describe($template, $description);
-            }
-        }
-
-        // describe routes that use the same URI template
-        elseif (func_num_args() === 2 && is_array($description)) {
-            foreach ($description as $method => $desc) {
-                $this->describe($uri_template, $desc, $method);
-            }
-        }
-
-        // describe a single route
-        else {
-            if (!isset($this->descriptions[$uri_template])) {
-                $this->descriptions[$uri_template] = [];
-            }
-            if (isset($this->routes[$method][$uri_template])) {
-                $this->descriptions[$uri_template][$method] = $description;
-            } else {
-                // Try to find route with different method
-                foreach ($this->routes as $m => $templates) {
-                    if (isset($templates[$uri_template])) {
-                        $this->descriptions[$uri_template][$m] = $description;
-                        break;
-                    }
-                }
-            }
-        }
-        return $this;
-    }
-
-    /**
-     * Get list of registered routes - optionally with their descriptions.
-     *
-     * @param bool $describe      (optional) include descriptions,
-     *                              defaults to `false`
-     * @param bool $check_access  (optional) only show methods this router's
-     *                              consumer is authorized to,
-     *                              defaults to `true`
-     *
-     * @return array list of registered routes
-     */
-    public function getRoutes($describe = false, $check_access = true)
-    {
-        $this->setupRoutes();
-
-        $result = [];
-        foreach ($this->routes as $method => $routes) {
-            foreach ($routes as $uri => $route) {
-                if ($check_access && !$this->permissions->check($uri, $method)) {
-                    continue;
-                }
-                if (!isset($result[$uri])) {
-                    $result[$uri] = [];
-                }
-                if ($describe) {
-                    $result[$uri][$method] = [
-                        'description' => $this->descriptions[$uri][$method] ?? null,
-                        'source'      => $route['source'] ?? 'unknown',
-                    ];
-                } else {
-                    $result[$uri][] = $method;
-                }
-            }
-        }
-        ksort($result);
-        if ($describe) {
-            $result = array_map(function ($item) {
-                ksort($item);
-                return $item;
-            }, $result);
-        }
-        return $result;
-    }
-
-    /**
-     * Dispatches an URI across the defined routes and produces a
-     * Response object which may then be send back (using #output).
-     *
-     * @param mixed  $uri     URI to dispatch (defaults to `$_SERVER['PATH_INFO']`)
-     * @param String $method  Request method (defaults to the method
-     *                        of the actual HTTP request or "GET")
-     *
-     * @return Response  a Response object containing status, headers
-     *                   and body
-     * @throws RouterException  may throw such an exception if there
-     *                          is no matching route (404) or if there
-     *                          is one, but the consumer is not
-     *                          authorized to it (403)
-     */
-    public function dispatch($uri = null, $method = null)
-    {
-        $this->setupRoutes();
-
-        $uri = $this->normalizeDispatchURI($uri);
-        $method = $this->normalizeRequestMethod($method);
-
-        $content_renderer = $this->negotiateContent($uri);
-
-        $match_result = $this->matchRoute($uri, $method, $content_renderer);
-        $route = $match_result[0];
-        $parameters = $match_result[1];
-        $allow_nobody = $match_result[2] ?? false;
-        if (!$route) {
-            //No route found for the combination of URI and method.
-            //We return the allowed methods for the route in the HTTP header:
-            $methods = $this->getMethodsForUri($uri);
-            if (count($methods) > 0) {
-                header('Allow: ' . implode(', ', $methods));
-                throw new RouterException(405);
-            } else {
-                //Route not found.
-                throw new RouterException(404);
-            }
-        }
-        //At this point, a route is found.
-        //We need to check if it can be used as nobody user or not.
-        if (!$route['allow_nobody'] && !$this->user) {
-            //Nobody users aren't allowed for this route.
-            throw new RouterException(401, 'Unauthorized (no consumer)');
-        }
-
-        try {
-            $response = $this->execute($route, $parameters);
-        } catch (RouterHalt $halt) {
-            $response = $halt->response;
-        }
-
-        $response->finish($content_renderer);
-
-        return $response;
-    }
-
-    /**
-     * Searches and registers available routes.
-     */
-    private function setupRoutes()
-    {
-        // A bit ugly, I confess
-        static $was_setup = false;
-        if ($was_setup) {
-            return;
-        }
-        $was_setup = true;
-
-        // Register default routes
-        $routes = [
-            'Activity',
-            'Blubber',
-            'Clipboard',
-            'Contacts',
-            'Course',
-            'Discovery',
-            'Events',
-			'Feedback',
-            'FileSystem',
-            'Forum',
-            'Messages',
-            'News',
-            'ResourceBooking',
-            'Resources',
-            'ResourceCategories',
-            'ResourcePermissions',
-            'ResourceProperties',
-            'ResourceRequest',
-            'RoomClipboard',
-            'Schedule',
-            'Semester',
-            'Studip',
-            'User',
-            'UserConfig',
-            'Wiki'
-        ];
-
-        foreach ($routes as $route) {
-            require_once "app/routes/$route.php";
-            $class = "\\RESTAPI\\Routes\\$route";
-            $this->registerRoutes(new $class);
-        }
-
-        // Register plugin routes
-        $router = $this;
-        $routes = array_flatten(\PluginEngine::sendMessage('RESTAPIPlugin', 'getRouteMaps'));
-        array_walk(
-            $routes,
-            function ($route) use ($router) {
-                $router->registerRoutes($route);
-            }
-        );
-    }
-
-    /**
-     * Takes a route and the parameters out of the requested path and
-     * executes the handler of the route.
-     *
-     * @param array $route      the matched route out of
-     *                          Router::matchRoute; an array with keys
-     *                          'handler', 'conditions' and 'source'
-     * @param array $parameters the matched parameters out of
-     *                          Router::matchRoute; something like:
-     *                          `array('user_id' => '23a21d...e78f')`
-     * @return Response  the resulting Response object which is then
-     *                   polished in Router::dispatch
-     */
-    protected function execute($route, $parameters)
-    {
-        $handler = $route['handler'];
-
-        if (!is_object($handler[0])) {
-            throw new \RuntimeException("Handler is not a method.");
-        }
-
-        $handler[0]->init($this, $route);
-
-        if (method_exists($handler[0], 'before')) {
-            $handler[0]->before($this, $handler, $parameters);
-        }
-
-        $result = call_user_func_array($handler, $parameters);
-
-        if (is_object($result) && method_exists($result, 'toArray')) {
-            $result = $result->toArray();
-        }
-
-        // $result is stronger than $response->body
-        if (isset($result)) {
-            $handler[0]->body($result);
-        }
-
-        if (method_exists($handler[0], 'after')) {
-            $handler[0]->after($this, $parameters);
-        }
-
-        return $handler[0]->getResponse();
-    }
-
-    /**
-     * Registers a content renderer.
-     *
-     * @param DefaultRenderer $renderer    instance of a content renderer
-     * @param boolean         $is_default  (optional) set this
-     *                                     renderer as default?;
-     *                                     defaults to `false`
-     *
-     * @return Router returns itself to allow chaining
-     */
-    public function registerRenderer($renderer, $is_default = false)
-    {
-        $this->renderers[$renderer->extension()] = $renderer;
-        if ($is_default) {
-            $this->default_renderer = $renderer;
-        }
-
-        return $this;
-    }
-
-    private function normalizeDispatchURI($uri)
-    {
-        return $uri ?? \Request::pathInfo();
-    }
-
-    private function normalizeRequestMethod($method)
-    {
-        return mb_strtolower($method ?: \Request::method() ?: 'get');
-    }
-
-    /**
-     * Negotiate content using the registered content renderers. The
-     * first ContentRenderer that returns `true` when calling
-     * ContentRenderer::shouldRespondTo gets the job.
-     *
-     * @param String $uri  the URI to which the content renderers may respond
-     *
-     * @return ContentRenderer  either a ContentRenderer that responds
-     *                          to the URI or the default
-     *                          ContentRenderer of this router.
-     */
-    protected function negotiateContent($uri)
-    {
-        $content_renderer = null;
-        foreach ($this->renderers as $renderer) {
-            if ($renderer->shouldRespondTo($uri)) {
-                $content_renderer = $renderer;
-                break;
-            }
-        }
-        if (!$content_renderer) {
-            $content_renderer = $this->default_renderer ?: reset($this->renderers);
-        }
-        return $content_renderer;
-    }
-
-    /**
-     * Tries to match a route given a URI and a HTTP request method.
-     *
-     * @param String $uri     the URI to match
-     * @param String $method  the HTTP request method to match
-     * @param DefaultRenderer $content_renderer the used
-     *                                          ContentRenderer which
-     *                                          is needed to remove
-     *                                          a file extension
-     *
-     * @return array  an array containing the matched route and the
-     *                found parameters
-     */
-    protected function matchRoute($uri, $method, $content_renderer)
-    {
-        $matched    = null;
-        $parameters = [];
-        if (isset($this->routes[$method])) {
-            if ($content_renderer->extension() && mb_strpos($uri, $content_renderer->extension()) !== false) {
-                $uri = mb_substr($uri, 0, -mb_strlen($content_renderer->extension()));
-            }
-
-            foreach ($this->routes[$method] as $uri_template => $route) {
-                if (!isset($route['uri_template'])) {
-                    $route['uri_template'] = new UriTemplate($uri_template, $route['conditions']);
-                }
-
-                $prmtrs = null; // Will be filled by a successful match()
-                if ($route['uri_template']->match($uri, $prmtrs)) {
-                    if (!$this->permissions->check($uri_template, $method)) {
-                        throw new RouterException(403, "Route not activated");
-                    }
-                    $matched = $route;
-                    $parameters = $prmtrs;
-                    break;
-                }
-            }
-        }
-        return [$matched, $parameters];
-    }
-
-    /**
-     * Returns all methods the given uri responds to.
-     *
-     * @param String $uri the URI to match
-     *
-     * @return array of all of responding methods
-     */
-    protected function getMethodsForUri($uri)
-    {
-        $methods = [];
-
-        foreach ($this->routes as $method => $templates) {
-            foreach ($templates as $uri_template => $route) {
-                if (!isset($route['uri_template'])) {
-                    $route['uri_template'] = new UriTemplate($uri_template, $route['conditions']);
-                }
-
-                if ($route['uri_template']->match($uri)
-                    && $this->permissions->check($uri_template, $method))
-                {
-                    $methods[] = $method;
-                }
-            }
-        }
-
-        return array_map('strtoupper', $methods);
-    }
-
-
-    /**
-     * Sets up the authentication for the router.
-     */
-    public function setupAuth()
-    {
-        // Detect consumer
-        $consumer = Consumer\Base::detectConsumer();
-        if (!$consumer) {
-            return null;
-        }
-
-        $this->user = $consumer->getUser();
-
-        // Set authentication if present
-        if ($this->user) {
-            // Skip fake authentication if user is already logged in
-            if ($GLOBALS['user']->id !== $this->user->id) {
-
-                $GLOBALS['auth'] = new \Seminar_Auth();
-                $GLOBALS['auth']->auth = [
-                    'uid'   => $this->user->user_id,
-                    'uname' => $this->user->username,
-                    'perm'  => $this->user->perms,
-                ];
-
-                $GLOBALS['user'] = new \Seminar_User($this->user);
-
-                $GLOBALS['perm'] = new \Seminar_Perm();
-                $GLOBALS['MAIL_VALIDATE_BOX'] = false;
-            }
-            setTempLanguage($GLOBALS['user']->id);
-        }
-
-        return $this->user;
-    }
-}
diff --git a/lib/classes/restapi/RouterException.php b/lib/classes/restapi/RouterException.php
deleted file mode 100644
index 1ce2afc..0000000
--- a/lib/classes/restapi/RouterException.php
+++ /dev/null
@@ -1,31 +0,0 @@
-<?php
-namespace RESTAPI;
-use \Exception;
-
-/**
- * Router exception.
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class RouterException extends Exception
-{
-    protected static $error_messages = [
-        400 => 'Bad Request',
-        401 => 'Unauthorized',
-        403 => 'Forbidden',
-        404 => 'Not Found',
-        405 => 'Method Not Allowed',
-        500 => 'Internal Server Error',
-        501 => 'Not implemented',
-    ];
-
-    public function __construct($code = 500, $message = '', $previous = null)
-    {
-        $message = $message ?: self::$error_messages[$code] ?: '';
-        parent::__construct($message, $code, $previous);
-    }
-}
diff --git a/lib/classes/restapi/RouterHalt.php b/lib/classes/restapi/RouterHalt.php
deleted file mode 100644
index 55a2ca1..0000000
--- a/lib/classes/restapi/RouterHalt.php
+++ /dev/null
@@ -1,19 +0,0 @@
-<?php
-namespace RESTAPI;
-
-/**
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class RouterHalt extends \Exception
-{
-    public $response;
-
-    public function __construct($response)
-    {
-        parent::__construct();
-        $this->response = $response;
-    }
-}
diff --git a/lib/classes/restapi/UriTemplate.php b/lib/classes/restapi/UriTemplate.php
deleted file mode 100644
index 67161de..0000000
--- a/lib/classes/restapi/UriTemplate.php
+++ /dev/null
@@ -1,115 +0,0 @@
-<?php
-namespace RESTAPI;
-
-/**
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class UriTemplate
-{
-    public $uri_template;
-    public $conditions;
-
-    public function __construct($uri_template, $conditions = [])
-    {
-        $this->uri_template = $uri_template;
-        $this->conditions = $conditions;
-    }
-
-    /**
-     * Tests whether an uri matches a template.
-     *
-     * The template may contain placeholders by prefixing an appropriate,
-     * unique placeholder name with a colon (:).
-     *
-     * <code>$template = '/hello/:name';</code>
-     *
-     * If the uri matches the template, all evaluated placeholders will
-     * be stored in the parameters array.
-     *
-     * @param String $uri        The uri to test
-     * @param array  $parameters Stores evaluated parameters on match (optional)
-     *
-     * @return bool Returns true if the uri matches the template
-     */
-    public function match($uri, &$parameters = null)
-    {
-        // Initialize parameters array
-        $parameters = [];
-
-        // Split and normalize uri and template
-        $given = array_filter(explode('/', $uri), 'mb_strlen');
-        $rules = array_filter(explode('/', $this->uri_template));
-
-        // Leave if uri and template do not contain the same number of
-        // elements
-        if (count($given) !== count($rules)) {
-            return false;
-        }
-
-        // Combine uri and template element-wise (simplifies iteration)
-        $combined = array_combine($rules, $given);
-
-        // Iterate over uri and template and compare element by element
-        foreach ($combined as $rule => $actual) {
-            if ($rule[0] === ':') {
-                // Rule is a placeholder
-                $parameter_name = mb_substr($rule, 1);
-
-                if (isset($this->conditions[$parameter_name])
-                    && !preg_match($this->conditions[$parameter_name], $actual)) {
-                    return false;
-                }
-
-                $parameters[$parameter_name] = $actual;
-
-            } elseif ($actual !== $rule) {
-                // Elements do not match
-                $parameters = [];
-                return false;
-            }
-        }
-
-        return true;
-    }
-
-
-    public function inject($params)
-    {
-        // Initialize parameters array
-        $parameters = [];
-
-        // Split and normalize template
-        $rules = array_filter(explode('/', $this->uri_template));
-
-        foreach ($rules as &$rule) {
-
-            // Rule is a placeholder
-            if ($rule[0] === ':') {
-                $parameter_name = mb_substr($rule, 1);
-
-                if (!isset($params[$parameter_name])) {
-                    $reason = sprintf('UriTemplate parameter :%s missing.',
-                                      htmlReady($parameter_name));
-                    throw new \RuntimeException($reason);
-                }
-
-                $actual = $params[$parameter_name];
-
-                if (isset($this->conditions[$parameter_name])
-                    && !preg_match($this->conditions[$parameter_name], $actual)) {
-                    $reason = sprintf('UriTemplate parameter :%s did not satisfy its condition.',
-                                      htmlReady($parameter_name));
-                    throw new \RuntimeException($reason);
-                }
-
-                $rule = htmlReady($actual);
-            }
-        }
-
-        return join('/', $rules);
-    }
-}
diff --git a/lib/classes/restapi/UserPermissions.php b/lib/classes/restapi/UserPermissions.php
deleted file mode 100644
index dcf1601..0000000
--- a/lib/classes/restapi/UserPermissions.php
+++ /dev/null
@@ -1,144 +0,0 @@
-<?php
-namespace RESTAPI;
-use DBManager, PDO;
-
-/**
- * REST API routing permissions
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @license    GPL 2 or later
- * @since      Stud.IP 2.6
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class UserPermissions
-{
-    /**
-     * Create a permission object (for a certain user).
-     * Permissions object will be cached for each user.
-     *
-     * @param mixed $user_id Id of user (optional, defaults to global)
-     * @return UserPermissions Returns permissions object
-     */
-    public static function get($user_id = null)
-    {
-        $user_id = $user_id ?: $GLOBALS['user']->id;
-
-        static $cache = [];
-        if (!isset($cache[$user_id])) {
-            $cache[$user_id] = new self($user_id);
-        }
-
-        return $cache[$user_id];
-    }
-
-    private $user_id;
-    private $permissions = [];
-
-    /**
-     * Creates the actual permission object (for a certain user).
-     *
-     * @param mixed $user_id Id of user (optional, defaults to global)
-     */
-    private function __construct($user_id = null)
-    {
-        $this->user_id = $user_id;
-
-        // Init with global permissions
-        $this->loadPermissions();
-    }
-
-    /**
-     * Defines whether access is allowed for the current user to the
-     * passed route via the passed method.
-     *
-     * @param String $user_id Id of the user
-     * @param mixed  $granted  Granted state (PHP'ish boolean)
-     * @return UserPermissions Returns instance of self to allow chaining
-     */
-    public function set($user_id, $granted = true)
-    {
-        $this->permissions[$user_id] = (bool)$granted;
-
-        return $this;
-    }
-
-    /**
-     * Loads permissions for passed user.
-     *
-     * @return UserPermissions Returns instance of self to allow chaining
-     */
-    protected function loadPermissions()
-    {
-        $query = "SELECT consumer_id, granted
-                  FROM api_user_permissions
-                  WHERE user_id = :user_id";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':user_id', $this->user_id);
-        $statement->execute();
-        $permissions = $statement->fetchAll(PDO::FETCH_ASSOC);
-
-        // Init with global permissions
-        foreach ($permissions as $permission) {
-            extract($permission);
-
-            $this->set($permission['consumer_id'], $permission['granted']);
-        }
-
-        return $this;
-    }
-
-    /**
-     * Checks if access to consumer is allowed for the current user.
-     *
-     * @param String $consumer_id  Id of the consumer
-     * @return bool Indicates whether access is allowed
-     */
-    public function check($consumer_id)
-    {
-        return isset($this->permissions[$consumer_id])
-            && $this->permissions[$consumer_id];
-    }
-
-    /**
-     * Stores the set permissions.
-     *
-     * @return bool Returns true if permissions were stored successfully
-     */
-    public function store()
-    {
-        $result = true;
-
-        $query = "INSERT INTO api_user_permissions (user_id, consumer_id, granted, mkdate, chdate)
-                  VALUES (:user_id, :consumer_id, :granted, UNIX_TIMESTAMP(), UNIX_TIMESTAMP())
-                  ON DUPLICATE KEY UPDATE granted = VALUES(granted),
-                                          chdate = UNIX_TIMESTAMP()";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':user_id', $this->user_id);
-
-        foreach ($this->permissions as $consumer_id => $granted) {
-            $statement->bindValue(':consumer_id', $consumer_id);
-            $statement->bindValue(':granted', (int) !empty($granted));
-
-            $result = $result && $statement->execute();
-        }
-
-        return $result;
-    }
-
-    /**
-     * Get a list of all consumer the user has granted acces to.
-     *
-     * @return array List of consumer objects
-     */
-    public function getConsumers()
-    {
-        $result = [];
-        foreach ($this->permissions as $consumer_id => $granted) {
-            if (!$granted) {
-                continue;
-            }
-            $result[$consumer_id] = Consumer\Base::find($consumer_id);
-        }
-        return $result;
-    }
-}
diff --git a/lib/classes/restapi/consumer/Base.php b/lib/classes/restapi/consumer/Base.php
deleted file mode 100644
index 50f3150..0000000
--- a/lib/classes/restapi/consumer/Base.php
+++ /dev/null
@@ -1,226 +0,0 @@
-<?php
-namespace RESTAPI\Consumer;
-
-use AuthUserMd5;
-use DBManager;
-use DBManagerException;
-use PDO;
-
-/**
- * Base consumer class for the rest api
- *
- * Consumers provide means for authenticating a user and the access
- * permissions for routes are bound to specific consumers.
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-abstract class Base extends \SimpleORMap
-{
-    /**
-     * Each consumer type has to implement a detect feature which
-     * should extract crucial information from the request and return
-     * an instance of itself if the consumer detects a valid signature
-     * it can respond to.
-     *
-     * @param mixed $request_type Type of request (optional; defaults to any)
-     * @return mixed Detected consumer object or false
-     */
-    abstract public static function detect($request_type = null);
-
-    /* Concrete */
-
-    /**
-     * Configures the model.
-     *
-     * @param array $config Configuration array
-     */
-    protected static function configure($config = [])
-    {
-        $config['db_table'] = 'api_consumers';
-
-        parent::configure($config);
-    }
-
-    /**
-     * Stores all known consumer types
-     */
-    protected static $known_types = [];
-
-    /**
-     * Add a consumer type to the list of consumer types
-     *
-     * @param String $type  Name of the type
-     * @param String $class Associated consumer class
-     */
-    public static function addType($type, $class)
-    {
-        self::$known_types[$type] = $class;
-    }
-
-    /**
-     * Removes a consumer type from the list of consumer types
-     *
-     * @param String $type Name of the type
-     */
-    public static function removeType($type)
-    {
-        unset(self::$known_types[$type]);
-    }
-
-    /**
-     * Overloaded find method. Will return a concrete specialized consumer
-     * object of the associated type.
-     *
-     * @param String $id Id of the consumer
-     * @return \RESTAPI\Consumer\Base Associated consumer object (derived
-     *                               from consumer base type)
-     * @throws \Exception if either consumer id or consumer type is invalid
-     */
-    public static function find($id)
-    {
-        $query = "SELECT consumer_type
-                  FROM api_consumers
-                  WHERE consumer_id = :id";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':id', $id);
-        $statement->execute();
-        $type = $statement->fetchColumn();
-
-        if (!isset(self::$known_types[$type])) {
-            throw new \Exception('Consumer #' . $id . ' is of unknown type "' . $type . '"');
-        }
-
-        return new self::$known_types[$type]($id);
-    }
-
-    /**
-     * Returns a list of all known consumers.
-     *
-     * @return array List of all known consumers (as specialized consumer
-     *               objects)
-     */
-    public static function findAll()
-    {
-        $query = "SELECT consumer_id FROM api_consumers";
-        $statement = DBManager::get()->query($query);
-        $ids = $statement->fetchAll(PDO::FETCH_COLUMN);
-
-        return array_map([self::class, 'find'], $ids);
-    }
-
-    /**
-     * Creates a new consumer of the given type.
-     *
-     * @param String $type Name of the type
-     * @return \RESTAPI\Consumer\Base Consumer object of the given (derived
-     *                               from consumer base type)
-     * @throws \Exception if type is invalid
-     */
-    public static function create($type)
-    {
-        if (!isset(self::$known_types[$type])) {
-            throw new \Exception('Consumer is of unknown type "' . $type . '"');
-        }
-
-        return new self::$known_types[$type];
-    }
-
-    /**
-     * This method is used to detect a consumer (of a specific type) by
-     * executing the detect method on all known consumer types.
-     *
-     * @param mixed $type Name of the type (optional; defaults to all types)
-     * @param mixed $request_type Type of request (optional; defaults to any)
-     * @return mixed Either the detected consumer or false if no consumer
-     *               was detected
-     * @throws \Exception if type is invalid
-     */
-    public static function detectConsumer($type = null, $request_type = null)
-    {
-        $needles = $type === null
-                 ? array_keys(self::$known_types)
-                 : [$type];
-        foreach ($needles as $needle) {
-            if (!isset(self::$known_types)) {
-                throw new \Exception('Trying to detect consumer of unkown type "' . $needle . '"');
-            }
-            $consumer_class = self::$known_types[$needle];
-            if ($consumer = $consumer_class::detect($request_type)) {
-                return $consumer;
-            }
-        }
-        return false;
-    }
-
-    /**
-     * Contains user information
-     */
-    protected $user = null;
-
-    /**
-     * Extended SimpleORMap constructor. A certain user can be injected upon
-     * creation.
-     *
-     * @param mixed $id Id of the consumer or null to create a new one
-     * @param mixed $user Either a user object or id to inject to the consumer
-     *                    or null if no user should be injected
-     */
-    public function __construct($id = null, $user = null)
-    {
-        parent::__construct($id);
-
-        if ($user !== null) {
-            $this->setUser($user);
-        }
-    }
-
-    /**
-     * Retrieve the api permissions associated with this consumer.
-     *
-     * @return \RESTAPI\ConsumerPermissions Permission object for this consumer
-     */
-    public function getPermissions()
-    {
-        return \RESTAPI\ConsumerPermissions::get($this->id);
-    }
-
-    /**
-     * Inject a user to this consumer. Injecting in this context refers to
-     * "having a user authenticated by this consumer".
-     *
-     * @param mixed $user Either a user object or a user id
-     * @return \RESTAPI\Consumer\Base Returns instance of self to allow
-     *                               chaining
-     */
-    public function setUser($user)
-    {
-        if (!is_object($user)) {
-            $user = \User::findFull($user);
-        }
-        $this->user = $user;
-        return $this;
-    }
-
-    /**
-     * Returns whether the consumer has an injected user or not.
-     *
-     * @return bool True if a valid user is found, false otherwise
-     */
-    public function hasUser()
-    {
-        return $this->user !== null && $this->user->id && $this->user->id !== 'nobody';
-    }
-
-    /**
-     * Return the injected user.
-     *
-     * @param mixed User object or false if no user was injected
-     */
-    public function getUser()
-    {
-        return $this->user;
-    }
-}
diff --git a/lib/classes/restapi/consumer/HTTP.php b/lib/classes/restapi/consumer/HTTP.php
deleted file mode 100644
index 97b0657..0000000
--- a/lib/classes/restapi/consumer/HTTP.php
+++ /dev/null
@@ -1,50 +0,0 @@
-<?php
-namespace RESTAPI\Consumer;
-use StudipAuthAbstract, RESTAPI\RouterException;
-
-/**
- * Basic HTTP Authentication consumer for the rest api
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class HTTP extends Base
-{
-    /**
-     * Detects if a user is authenticated via basic http authentication.
-     * The only supported authentication for now is via the url:
-     *
-     * http://username:password@host/path?query
-     *
-     * @param mixed $request_type Type of request (optional; defaults to any)
-     * @return mixed Instance of self if authentication was detected, false
-     *               otherwise
-     * @throws RouterException if authentication fails
-     * @todo Integrate and test HTTP_AUTHORIZATION header authentication
-     */
-    public static function detect($request_type = null)
-    {
-        if (
-            isset($_SERVER['PHP_AUTH_USER'], $_SERVER['PHP_AUTH_PW'])
-            || isset($_SERVER['HTTP_AUTHORIZATION'])
-        ) {
-            $user_id = false;
-
-            if (isset($_SERVER['PHP_AUTH_USER'], $_SERVER['PHP_AUTH_PW'])) {
-                $username = $_SERVER['PHP_AUTH_USER'];
-                $password = $_SERVER['PHP_AUTH_PW'];
-            } elseif (isset($_SERVER['HTTP_AUTHORIZATION'])) {
-                list($username, $password) = explode(':', base64_decode(mb_substr($_SERVER['HTTP_AUTHORIZATION'], 6)));
-            }
-
-            $check = StudipAuthAbstract::CheckAuthentication($username, $password);
-            if ($check['uid'] && $check['uid'] !== 'nobody') {
-                return new self(null, $check['uid']);
-            }
-
-        }
-        return false;
-    }
-}
diff --git a/lib/classes/restapi/consumer/OAuth.php b/lib/classes/restapi/consumer/OAuth.php
deleted file mode 100644
index caf51c2..0000000
--- a/lib/classes/restapi/consumer/OAuth.php
+++ /dev/null
@@ -1,231 +0,0 @@
-<?php
-namespace RESTAPI\Consumer;
-use StudipAutoloader, DBManager, OAuthRequestVerifier, OAuthStore, OAuthServer, Exception;
-use \RESTAPI\UserPermissions;
-
-StudipAutoloader::addAutoloadPath($GLOBALS['STUDIP_BASE_PATH'] . DIRECTORY_SEPARATOR . 'vendor/oauth-php/library/');
-
-/**
- * OAuth consumer for the rest api
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class OAuth extends Base
-{
-    /**
-     * Configures the model.
-     *
-     * @param array $config Configuration array
-     */
-    protected static function configure($config = [])
-    {
-        $config['default_values']['consumer_type'] = 'oauth';
-
-        $config['registered_callbacks']['before_store'][] = 'before_store';
-
-        parent::configure($config);
-    }
-
-    /**
-     * Detects whether the request is authenticated via OAuth.
-     *
-     * @param mixed $request_type Type of request (optional; defaults to any)
-     * @return mixed Instance of self if authentication was detected, false
-     *               otherwise
-     */
-    public static function detect($request_type = null)
-    {
-        if (OAuthRequestVerifier::requestIsSigned() && $request_type !== 'request') {
-            $user_id = false;
-
-            $parameters = (in_array($_SERVER['REQUEST_METHOD'], ['GET', 'POST']))
-                        ? null
-                        : $GLOBALS['_' . $_SERVER['REQUEST_METHOD']];
-
-            $req = new OAuthRequestVerifier(null, null, $parameters);
-
-            // Check oauth timestamp and deny access if timestamp is outdated
-            if ($req->getParam('oauth_timestamp') < strtotime('-6 hours')) {
-                return false;
-            }
-            $result = $req->verifyExtended('access');
-
-            // @todo
-            # self::$consumer_key = $result['consumer_key'];
-
-            $query = "SELECT user_id FROM api_oauth_user_mapping WHERE oauth_id = :oauth_id";
-            $statement = DBManager::get()->prepare($query);
-            $statement->bindValue(':oauth_id', $result['user_id']);
-            $statement->execute();
-            $user_id = $statement->fetchColumn();
-
-            if (!$user_id) {
-                return false;
-            }
-
-            $consumer = reset(self::findByAuth_Key($result['consumer_key']));
-            $consumer->setUser($user_id);
-            return $consumer;
-        } else {
-            try {
-                // Check if there is a valid request token in the current request
-                // Returns an array with the consumer key, consumer secret, token, token secret and token type.
-                $rs = self::getServer()->authorizeVerify();
-
-                $query = "SELECT consumer_id
-                          FROM api_consumers
-                          WHERE auth_key = :key";
-                $statement = DBManager::get()->prepare($query);
-                $statement->bindValue(':key', $rs['consumer_key']);
-                $statement->execute();
-                $id = $statement->fetchColumn();
-
-                if ($id) {
-                    return new self($id);
-                }
-            } catch (Exception $e) {
-            }
-        }
-        return false;
-    }
-
-    /**
-     * Returns a singleton instance of the oauth server.
-     *
-     * @return OAuthServer The server object
-     */
-    public static function getServer()
-    {
-        static $server = null;
-        if ($server === null) {
-            $server = new OAuthServer(null, null, null, 'SESSION', [], [
-                'allowed_uri_schemes' => []
-            ]);
-        }
-        return $server;
-    }
-
-    /**
-     * "Before store" trigger. Creates a clone of the consumer in the
-     * tables for the vendor oauth library.
-     */
-    protected function before_store()
-    {
-        static $mapping = [
-            'auth_key'    => 'consumer_key',
-            'auth_secret' => 'consumer_secret',
-            'active'      => 'enabled',
-            'contact'     => 'requester_name',
-            'email'       => 'requester_email',
-            'callback'    => 'callback_uri',
-            'url'         => 'application_uri',
-            'title'       => 'application_title',
-            'description' => 'application_descr',
-            'notes'       => 'application_notes',
-            'type'        => 'application_type',
-            'commercial'  => 'application_commercial',
-        ];
-
-        $consumer = [];
-        foreach ($mapping as $from => $to) {
-            $consumer[$to] = $this->$from;
-        }
-
-        $query = "SELECT osr_id
-                  FROM oauth_server_registry
-                  WHERE osr_consumer_key = :key AND osr_consumer_secret = :secret";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':key', $this->auth_key);
-        $statement->bindValue(':secret', $this->auth_secret);
-        $statement->execute();
-        $consumer['id'] = $statement->fetchColumn();
-
-        $consumer_key = OAuthStore::instance('PDO')->updateConsumer($consumer, null, true);
-
-        if ($this->isNew()) {
-            $consumer = OAuthStore::instance('PDO')->getConsumer($consumer_key, null, true);
-            $this->auth_key    = $consumer['consumer_key'];
-            $this->auth_secret = $consumer['consumer_secret'];
-        }
-    }
-
-    /**
-     * Grant oauth access for a user.
-     *
-     * @param mixed $user_id Specific user id or null to default to the
-     *                       injected user
-     * @throws Exception If no valid user is present
-     */
-    public function grantAccess($user_id = null)
-    {
-        if ($user_id === null && $this->hasUser()) {
-            $user_id = $this->user->id;
-        }
-        if (!$user_id) {
-            throw new Exception('Can not grant access to unknown user');
-        }
-
-        UserPermissions::get($GLOBALS['user']->id)->set($this->id, true)->store();
-        return self::getServer()->authorizeFinish(true, self::getOAuthId($user_id));
-    }
-
-    /**
-     * Revoke oauth access from a user.
-     *
-     * @param mixed $user_id Specific user id or null to default to the
-     *                       injected user
-     * @throws Exception If no valid user is present
-     */
-    public function revokeAccess($user_id = null)
-    {
-        if ($user_id === null && $this->hasUser()) {
-            $user_id = $this->user->id;
-        }
-        if (!$user_id) {
-            throw new Exception('Can not revoke access from unknown user');
-        }
-
-        $query = "DELETE oauth_server_token
-                  FROM oauth_server_token
-                  JOIN oauth_server_registry
-                  WHERE ost_usa_id_ref = :id AND osr_consumer_key = :key AND osr_consumer_secret = :secret";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':id', self::getOAuthId($user_id));
-        $statement->bindValue(':key', $this->auth_key);
-        $statement->bindValue(':secret', $this->auth_secret);
-        $statement->execute();
-
-        UserPermissions::get($GLOBALS['user']->id)->set($this->id, false)->store();
-        return self::getServer()->authorizeFinish(false, self::getOAuthId($user_id));
-    }
-
-    /**
-     * Maps a user to an oauth id. This is neccessary due to the fact that
-     * the oauth lib works with different ids than Stud.IP.
-     *
-     * @param String $user_id Id of the user to get an oauth id for
-     * @return String The mapped oauth id
-     */
-    public static function getOAuthId($user_id)
-    {
-        $query = "SELECT oauth_id FROM api_oauth_user_mapping WHERE user_id = :id";
-        $statement = DBManager::get()->prepare($query);
-        $statement->bindValue(':id', $user_id);
-        $statement->execute();
-        $oauth_id = $statement->fetchColumn();
-
-        if (!$oauth_id) {
-            $query = "INSERT INTO api_oauth_user_mapping (user_id, mkdate)
-                      VALUES (:id, UNIX_TIMESTAMP())";
-            $statement = DBManager::get()->prepare($query);
-            $statement->bindValue(':id', $user_id);
-            $statement->execute();
-            $oauth_id = DBManager::get()->lastInsertId();
-        }
-
-        return $oauth_id;
-    }
-}
diff --git a/lib/classes/restapi/consumer/Studip.php b/lib/classes/restapi/consumer/Studip.php
deleted file mode 100644
index 738dd75..0000000
--- a/lib/classes/restapi/consumer/Studip.php
+++ /dev/null
@@ -1,36 +0,0 @@
-<?php
-namespace RESTAPI\Consumer;
-
-/**
- * Stud.IP Session Consumer for the rest api
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class Studip extends Base
-{
-    /**
-     * Detects a user via the Stud.IP session. If a session is present and
-     * valid, the auth and user object have already been set up by stud.ip
-     * functions, so we just need to check if these are present.
-     *
-     * @param mixed $request_type Type of request (optional; defaults to any)
-     * @return mixed Instance of self if authentication was detected, false
-     *               otherwise
-     */
-    public static function detect($request_type = null)
-    {
-        if (
-            !isset($GLOBALS['auth'])
-            || !$GLOBALS['auth']->is_authenticated()
-            || $GLOBALS['user']->id === 'nobody'
-            || !\CSRFProtection::verifyRequest()
-        ) {
-            return false;
-        }
-
-        return new self(null, $GLOBALS['user']->id);
-    }
-}
diff --git a/lib/classes/restapi/renderer/DebugRenderer.php b/lib/classes/restapi/renderer/DebugRenderer.php
deleted file mode 100644
index afd56f6..0000000
--- a/lib/classes/restapi/renderer/DebugRenderer.php
+++ /dev/null
@@ -1,57 +0,0 @@
-<?php
-namespace RESTAPI\Renderer;
-
-/**
- * Debug content renderer.
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class DebugRenderer extends DefaultRenderer
-{
-    /**
-     * Returns an associated content type.
-     */
-    public function contentType()
-    {
-        return 'text/plain';
-    }
-
-    /**
-     * Returns an associated extension.
-     */
-    public function extension()
-    {
-        return '.debug';
-    }
-
-    /**
-     * Response transformation function.
-     *
-     * @param \RESTAPI\Response $response  the response to transform
-     */
-    public function render($response)
-    {
-        if (!isset($response['Content-Type'])) {
-            $response['Content-Type'] = $this->contentType() . ';charset=utf-8';
-        }
-
-        $debug = function ($label, $data) {
-            echo str_pad('', 78, '=') . PHP_EOL;
-            echo str_pad('- ' . $label, 77, ' ') . '-' . PHP_EOL;
-            echo str_pad('', 78, '=') . PHP_EOL;
-            var_export($data);
-            echo PHP_EOL;
-        };
-
-        ob_start();
-        $debug('Response Status', $response->status);
-        $debug('Response Header', $response->headers);
-        $debug('Response Body',   $response->body);
-        $debug('Request', $GLOBALS['_' . $_SERVER['REQUEST_METHOD']]);
-        $response->body = ob_get_clean();
-    }
-}
diff --git a/lib/classes/restapi/renderer/DefaultRenderer.php b/lib/classes/restapi/renderer/DefaultRenderer.php
deleted file mode 100644
index 836ba36..0000000
--- a/lib/classes/restapi/renderer/DefaultRenderer.php
+++ /dev/null
@@ -1,74 +0,0 @@
-<?php
-namespace RESTAPI\Renderer;
-
-/**
- * Default base content renderer class (outputs text/plain).
- *
- * Content renderers are output filters that can reshape data before it
- * is sent to the client.
- * Each content renderer is associated with a certain content type and a
- * certain file extension. This is neccessary for content negotiation.
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class DefaultRenderer
-{
-    /**
-     * Returns an associated content type.
-     *
-     * @return String Content/mime type for this renderer
-     */
-    public function contentType()
-    {
-        return 'text/plain';
-    }
-
-    /**
-     * Returns an associated extension.
-     *
-     * @return String Associated extension for this renderer.
-     */
-    public function extension()
-    {
-        return '';
-    }
-
-    /**
-     * Response transformation function.
-     *
-     * @param \RESTAPI\Response $response  the response to transform
-     */
-    public function render($response)
-    {
-        if (!isset($response['Content-Type'])) {
-            $response['Content-Type'] = $this->contentType() . ';charset=utf-8';
-        }
-    }
-
-    /**
-     * Detects whether the renderer should respond to either a certain
-     * filename (tests by extension) or to a certain media range.
-     *
-     * @param String $filename    Filename to test against
-     * @param mixed  $media_range Media range to test against (optional,
-     *                            defaults to request's accept header if set)
-     * @return bool Returns whether the renderer should respond
-     */
-    public function shouldRespondTo($filename, $media_range = null)
-    {
-        // If no media range is passed, evalute http header "Accept"
-        if ($media_range === null && isset($_SERVER['ACCEPT'])) {
-            $media_ranges = explode(';', $_SERVER['ACCEPT']);
-            $media_range = reset($media_ranges);
-        }
-
-        // Test if either the filename has the appropriate extension or
-        // if the client accepts the content type
-        return ($this->extension() && fnmatch('*' . $this->extension(), $filename))
-            || ($media_range && fnmatch($media_range, $this->contentType()));
-    }
-}
diff --git a/lib/classes/restapi/renderer/JSONRenderer.php b/lib/classes/restapi/renderer/JSONRenderer.php
deleted file mode 100644
index 9c6e449..0000000
--- a/lib/classes/restapi/renderer/JSONRenderer.php
+++ /dev/null
@@ -1,35 +0,0 @@
-<?php
-namespace RESTAPI\Renderer;
-
-/**
- * Content renderer for json content.
- *
- * @author     Jan-Hendrik Willms <tleilax+studip@gmail.com>
- * @author     <mlunzena@uos.de>
- * @license    GPL 2 or later
- * @since      Stud.IP 3.0
- * @deprecated Since Stud.IP 5.0. Will be removed in Stud.IP 6.0.
- */
-class JSONRenderer extends DefaultRenderer
-{
-    public function contentType()
-    {
-        return 'application/json';
-    }
-
-    public function extension()
-    {
-        return '.json';
-    }
-
-    public function render($response)
-    {
-        if (!isset($response['Content-Type'])) {
-            $response['Content-Type'] = $this->contentType() . ';charset=utf-8';
-        }
-
-        if (isset($response->body)) {
-            $response->body = json_encode($response->body);
-        }
-    }
-}
diff --git a/lib/classes/searchtypes/MyCoursesSearch.class.php b/lib/classes/searchtypes/MyCoursesSearch.php
index 64bee64..1bdb250 100644
--- a/lib/classes/searchtypes/MyCoursesSearch.class.php
+++ b/lib/classes/searchtypes/MyCoursesSearch.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * MyCoursesSearch.class.php
+ * MyCoursesSearch.php
  * Search only in own courses.
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/searchtypes/NewsRangesSearch.php b/lib/classes/searchtypes/NewsRangesSearch.php
index 458d6f0..6cb7a2f 100644
--- a/lib/classes/searchtypes/NewsRangesSearch.php
+++ b/lib/classes/searchtypes/NewsRangesSearch.php
@@ -56,7 +56,7 @@ class NewsRangesSearch extends SearchType
                                    LEFT JOIN `semester_courses` AS sc ON s.`Seminar_id` = sc.`course_id`
                                    LEFT JOIN `semester_data` USING (`semester_id`)
                                    WHERE {$sem_inst}.`institut_id` IN (:institutes)
-                                     AND `name` LIKE :input
+                                     AND s.`name` LIKE :input
                                    GROUP BY s.`Seminar_id`
                                    ORDER BY s.`start_time` DESC
                                ) AS course_select";
diff --git a/lib/classes/searchtypes/PermissionSearch.class.php b/lib/classes/searchtypes/PermissionSearch.php
index cc4ce3e..3f86271 100644
--- a/lib/classes/searchtypes/PermissionSearch.class.php
+++ b/lib/classes/searchtypes/PermissionSearch.php
@@ -12,7 +12,7 @@
 
 /**
  * Class of type SearchType used for searches with QuickSearch
- * (lib/classes/QuickSearch.class.php). You can search for people with a given
+ * (lib/classes/QuickSearch.php). You can search for people with a given
  * Stud.IP permission level, either globally or at an institute.
  *
  * @author Thomas Hackl
diff --git a/lib/classes/searchtypes/RangeSearch.class.php b/lib/classes/searchtypes/RangeSearch.php
index caefae0..caefae0 100644
--- a/lib/classes/searchtypes/RangeSearch.class.php
+++ b/lib/classes/searchtypes/RangeSearch.php
diff --git a/lib/classes/searchtypes/ResourceSearch.class.php b/lib/classes/searchtypes/ResourceSearch.php
index 24038a8..f664beb 100644
--- a/lib/classes/searchtypes/ResourceSearch.class.php
+++ b/lib/classes/searchtypes/ResourceSearch.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * ResourceSearch.class.php - A search type for resources.
+ * ResourceSearch.php - A search type for resources.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
diff --git a/lib/classes/searchtypes/RoomSearch.class.php b/lib/classes/searchtypes/RoomSearch.php
index 002712e..877c2cb 100644
--- a/lib/classes/searchtypes/RoomSearch.class.php
+++ b/lib/classes/searchtypes/RoomSearch.php
@@ -1,7 +1,7 @@
 <?php
 
 /**
- * RoomSearch.class.php - A search type for rooms.
+ * RoomSearch.php - A search type for rooms.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
diff --git a/lib/classes/searchtypes/SQLSearch.class.php b/lib/classes/searchtypes/SQLSearch.php
index 86aff6d..de4efa3 100644
--- a/lib/classes/searchtypes/SQLSearch.class.php
+++ b/lib/classes/searchtypes/SQLSearch.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /**
- * SQLSearch.class.php - Class of type SearchType used for searches with QuickSearch
+ * SQLSearch.php - Class of type SearchType used for searches with QuickSearch
  *
  * Long description for file (if any)...
  *
@@ -17,7 +17,7 @@
 
 /**
  * Class of type SearchType used for searches with QuickSearch
- * (lib/classes/QuickSearch.class.php). You can search with a sql-syntax in the
+ * (lib/classes/QuickSearch.php). You can search with a sql-syntax in the
  * database. You just need to give in a query like for a PDB-prepare statement
  * and at least the variable ":input" in the query (the :input will be replaced
  * with the input of the QuickSearch userinput.
diff --git a/lib/classes/searchtypes/SearchType.class.php b/lib/classes/searchtypes/SearchType.php
index d46d57e..b4f9b68 100644
--- a/lib/classes/searchtypes/SearchType.class.php
+++ b/lib/classes/searchtypes/SearchType.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /**
- * SQLSearch.class.php - A class-structure for alle search-objects in Stud.IP.
+ * SQLSearch.php - A class-structure for alle search-objects in Stud.IP.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -104,4 +104,3 @@ abstract class SearchType
      */
     abstract public function includePath();
 }
-
diff --git a/lib/classes/searchtypes/SeminarSearch.class.php b/lib/classes/searchtypes/SeminarSearch.php
index e490228..fd7bf8a 100644
--- a/lib/classes/searchtypes/SeminarSearch.class.php
+++ b/lib/classes/searchtypes/SeminarSearch.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /**
- * SeminarSearch.class.php
+ * SeminarSearch.php
  * class to adapt StudipSemSearch to Quicksearch
  *
  * This program is free software; you can redistribute it and/or
diff --git a/lib/classes/searchtypes/StandardSearch.class.php b/lib/classes/searchtypes/StandardSearch.php
index 837a849..a3f0f3b 100644
--- a/lib/classes/searchtypes/StandardSearch.class.php
+++ b/lib/classes/searchtypes/StandardSearch.php
@@ -1,7 +1,7 @@
 <?php
 # Lifter010: TODO
 /**
- * StandardSearch.class.php - Class of type SearchType used for searches with QuickSearch
+ * StandardSearch.php - Class of type SearchType used for searches with QuickSearch
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
@@ -15,7 +15,7 @@
 
 /**
  * Class of type SearchType used for searches with QuickSearch
- * (lib/classes/QuickSearch.class.php). You can search with a sql-syntax in the
+ * (lib/classes/QuickSearch.php). You can search with a sql-syntax in the
  * database. You just need to give in a query like for a PDB-prepare statement
  * and at least the variable ":input" in the query (the :input will be replaced
  * with the input of the QuickSearch userinput.
diff --git a/lib/classes/searchtypes/TreeSearch.class.php b/lib/classes/searchtypes/TreeSearch.php
index 2fecf60..73d4239 100644
--- a/lib/classes/searchtypes/TreeSearch.class.php
+++ b/lib/classes/searchtypes/TreeSearch.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * TreeSearch.class.php - Class of type SearchType used for searches with QuickSearch
+ * TreeSearch.php - Class of type SearchType used for searches with QuickSearch
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
diff --git a/lib/classes/sidebar/AttributesArrayAccessTrait.php b/lib/classes/sidebar/AttributesArrayAccessTrait.php
index 7bea834..09fc030 100644
--- a/lib/classes/sidebar/AttributesArrayAccessTrait.php
+++ b/lib/classes/sidebar/AttributesArrayAccessTrait.php
@@ -3,41 +3,25 @@ trait AttributesArrayAccessTrait
 {
     public $attributes = [];
 
-    /**
-     * @todo Add bool return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetExists($offset)
+    public function offsetExists($offset): bool
     {
         return isset($this->attributes[$offset]);
     }
 
     /**
-     * @param $offset
-     * @return mixed
-     *
-     * @todo Add mixed return type when Stud.IP requires PHP8 minimal
+     * @param string $offset
      */
-    #[ReturnTypeWillChange]
-    public function offsetGet($offset)
+    public function offsetGet($offset): mixed
     {
         return $this->attributes[$offset];
     }
 
-    /**
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetSet($offset, $value)
+    public function offsetSet($offset, $value): void
     {
         $this->attributes[$offset] = $value;
     }
 
-    /**
-     * @todo Add void return type when Stud.IP requires PHP8 minimal
-     */
-    #[ReturnTypeWillChange]
-    public function offsetUnset($offset)
+    public function offsetUnset($offset): void
     {
         unset($this->attributes[$offset]);
     }
diff --git a/lib/classes/sidebar/ClipboardWidget.class.php b/lib/classes/sidebar/ClipboardWidget.php
index abc0d6c..abc0d6c 100644
--- a/lib/classes/sidebar/ClipboardWidget.class.php
+++ b/lib/classes/sidebar/ClipboardWidget.php
diff --git a/lib/classes/sidebar/InstituteSelectWidget.class.php b/lib/classes/sidebar/InstituteSelectWidget.php
index ec05311..ec05311 100644
--- a/lib/classes/sidebar/InstituteSelectWidget.class.php
+++ b/lib/classes/sidebar/InstituteSelectWidget.php
diff --git a/lib/classes/sidebar/LinksWidget.php b/lib/classes/sidebar/LinksWidget.php
index bc8256d..72a2fca 100644
--- a/lib/classes/sidebar/LinksWidget.php
+++ b/lib/classes/sidebar/LinksWidget.php
@@ -30,7 +30,7 @@ class LinksWidget extends ListWidget
     public function &addLink($label, $url, $icon = null, $attributes = [], $index = null)
     {
         if ($index === null) {
-            $index = 'link-' . md5($url);
+            $index = 'link-' . md5($url . $label);
         }
         $element = new LinkElement($label, $url, $icon, $attributes);
         $this->addElement($element, $index);
diff --git a/lib/classes/sidebar/ResourceTreeWidget.class.php b/lib/classes/sidebar/ResourceTreeWidget.php
index 60d4b29..60d4b29 100644
--- a/lib/classes/sidebar/ResourceTreeWidget.class.php
+++ b/lib/classes/sidebar/ResourceTreeWidget.php
diff --git a/lib/classes/sidebar/RoomClipboardWidget.class.php b/lib/classes/sidebar/RoomClipboardWidget.php
index 3d90c36..3d90c36 100644
--- a/lib/classes/sidebar/RoomClipboardWidget.class.php
+++ b/lib/classes/sidebar/RoomClipboardWidget.php
diff --git a/lib/classes/sidebar/RoomSearchTreeWidget.class.php b/lib/classes/sidebar/RoomSearchTreeWidget.php
index c3aaa07..c3aaa07 100644
--- a/lib/classes/sidebar/RoomSearchTreeWidget.class.php
+++ b/lib/classes/sidebar/RoomSearchTreeWidget.php
diff --git a/lib/classes/sidebar/RoomSearchWidget.class.php b/lib/classes/sidebar/RoomSearchWidget.php
index 1fa465f..1fa465f 100644
--- a/lib/classes/sidebar/RoomSearchWidget.class.php
+++ b/lib/classes/sidebar/RoomSearchWidget.php
diff --git a/lib/classes/sidebar/Sidebar.php b/lib/classes/sidebar/Sidebar.php
index 65fc62d..ba1e609 100644
--- a/lib/classes/sidebar/Sidebar.php
+++ b/lib/classes/sidebar/Sidebar.php
@@ -186,7 +186,7 @@ class Sidebar extends WidgetContainer
         static $actions_widget_added = false;
 
 
-        if ($widget instanceof NavigationWidget && !$navigation_widget_added) {
+        if ($widget instanceof NavigationWidget && !$navigation_widget_added && $widget->hasElements()) {
             SkipLinks::addIndex(
                 _('Dritte Navigationsebene'),
                 $widget->getId(),
@@ -197,7 +197,7 @@ class Sidebar extends WidgetContainer
             $navigation_widget_added = true;
         }
 
-        if ($widget instanceof ActionsWidget && !$actions_widget_added) {
+        if ($widget instanceof ActionsWidget && !$actions_widget_added && $widget->hasElements()) {
             if (!$widget->getId()) {
                 $widget->setId('sidebar-actions');
             }
diff --git a/lib/classes/sidebar/TemplateWidget.php b/lib/classes/sidebar/TemplateWidget.php
index c937c3b..2ca2d70 100644
--- a/lib/classes/sidebar/TemplateWidget.php
+++ b/lib/classes/sidebar/TemplateWidget.php
@@ -15,10 +15,10 @@ class TemplateWidget extends SidebarWidget
      * Constructor of the widget.
      *
      * @param String         $title     Title of the widget
-     * @param Flexi_Template $template  Template for the widget
+     * @param Flexi\Template $template  Template for the widget
      * @param array          $variables Associated variables for the template
      */
-    public function __construct($title, Flexi_Template $template, array $variables = [])
+    public function __construct($title, Flexi\Template $template, array $variables = [])
     {
         parent::__construct();