public function up()
 {
     // Namespace Classes
     $this->renameClass('CalendarEntry', CalendarEntry::className());
     $this->renameClass('CalendarEntryParticipant', CalendarEntryParticipant::className());
     // Merge EntryCreated to ContentCreated Activity
     $this->update('activity', ['class' => 'humhub\\modules\\content\\activities\\ContentCreated'], ['class' => 'EntryCreated']);
     $this->update('activity', ['class' => \humhub\modules\calendar\activities\ResponseAttend::className()], ['class' => 'EntryResponseAttend']);
     $this->update('activity', ['class' => \humhub\modules\calendar\activities\ResponseDeclined::className()], ['class' => 'EntryResponseDeclined']);
     $this->update('activity', ['class' => \humhub\modules\calendar\activities\ResponseMaybe::className()], ['class' => 'EntryResponseMaybe']);
 }
 public function getCalendarEntry()
 {
     return $this->hasOne(CalendarEntry::className(), ['id' => 'calendar_entry_id']);
 }