personal calendar: added "manage groups" action in sidebar, closes #3629

Closes #3629

Merge request studip/studip!2563

app/controllers/calendar/calendar.php

@@ -68,6 +68,11 @@ class Calendar_CalendarController extends AuthenticatedController
                 Icon::create('share'),
                 ['data-dialog' => 'size=default']
             );
+            $actions->addLink(
+                _('Gruppen verwalten'),
+                $this->url_for('contact/index'),
+                Icon::create('group2')
+            );
         }
         $actions->addLink(
             _('Drucken'),