remove forum abos and favorites upon user deletion and add a migration that...

remove forum abos and favorites upon user deletion and add a migration that cleans up the current state in the tables, fixes #2289

Closes #2289

Merge request studip/studip!1513

db/migrations/5.1.43_cleanup_forum_tables.php

+<?php
+final class CleanupForumTables extends Migration
+{
+    protected function up()
+    {
+        $query = "DELETE FROM `forum_abo_users`
+                  WHERE `user_id` NOT IN (
+                      SELECT `user_id`
+                      FROM `auth_user_md5`
+                  )";
+        DBManager::get()->exec($query);
+
+        $query = "DELETE FROM `forum_favorites`
+                  WHERE `user_id` NOT IN (
+                      SELECT `user_id`
+                      FROM `auth_user_md5`
+                  )";
+        DBManager::get()->exec($query);
+    }
+}

lib/classes/UserManagement.class.php

@@ -1187,6 +1187,8 @@ class UserManagement
             "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 = ?",
+            "DELETE FROM forum_favorites WHERE user_id = ?",
 
             "DELETE FROM comments WHERE user_id = ?",
             "DELETE questionnaires FROM questionnaires LEFT JOIN questionnaire_assignments qa USING (`questionnaire_id`) WHERE qa.range_id = ?",