drop table blubber_follower and remove last remaining code for it, fixes #2082

Closes #2082

Merge request studip/studip!1353

db/migrations/5.1.40_drop_table_blubber_follower.php

+<?php
+
+/**
+ * @see https://gitlab.studip.de/studip/studip/-/issues/2082
+ */
+final class DropTableBlubberFollower extends Migration
+{
+    public function description()
+    {
+        return 'Removes unused table "blubber_follower"';
+    }
+
+    protected function up()
+    {
+        $query = "DROP TABLE IF EXISTS `blubber_follower`";
+        DBManager::get()->exec($query);
+    }
+
+    protected function down()
+    {
+        $query = "CREATE TABLE IF NOT EXISTS `blubber_follower` (
+                    `studip_user_id` CHAR(32) COLLATE latin1_bin NOT NULL,
+                    `external_contact_id` CHAR(32) COLLATE latin1_bin NOT NULL,
+                    `left_follows_right` TINYINT(1) UNSIGNED NOT NULL DEFAULT 0,
+                    KEY `studip_user_id` (`studip_user_id`),
+                    KEY `external_contact_id` (`external_contact_id`)
+                  )";
+        DBManager::get()->exec($query);
+    }
+}

lib/models/User.class.php

@@ -1258,9 +1258,6 @@ class User extends AuthUserMd5 implements Range, PrivacyObject
         $query = "UPDATE IGNORE blubber_comments SET user_id = ? WHERE user_id = ?";
         $statement = DBManager::get()->prepare($query);
         $statement->execute([$new_id, $old_id]);
-        $query = "UPDATE IGNORE blubber_follower SET studip_user_id = ? WHERE studip_user_id = ?";
-        $statement = DBManager::get()->prepare($query);
-        $statement->execute([$new_id, $old_id]);
         $query = "UPDATE IGNORE blubber_mentions SET user_id = ? WHERE user_id = ?";
         $statement = DBManager::get()->prepare($query);
         $statement->execute([$new_id, $old_id]);