/**
  * delete multiple entries
  */
 public function delete()
 {
     if (!isset($_POST['apps'])) {
         ilUtil::sendFailure($this->lng->txt('select_one'));
         return $this->appointmentList();
     }
     include_once 'Services/Calendar/classes/class.ilCalendarEntry.php';
     include_once 'Services/Calendar/classes/class.ilCalendarCategoryAssignments.php';
     foreach ($_POST['apps'] as $entry_id) {
         // cancel booking for users
         $booking = ilBookingEntry::getInstanceByCalendarEntryId($entry_id);
         if ($booking) {
             foreach ($booking->getCurrentBookings($entry_id) as $user_id) {
                 include_once './Services/Calendar/classes/ConsultationHours/class.ilConsultationHourUtils.php';
                 ilConsultationHourUtils::cancelBooking($user_id, $entry_id, false);
             }
         }
         // remove calendar entries
         include_once './Services/Calendar/classes/class.ilCalendarEntry.php';
         $entry = new ilCalendarEntry($entry_id);
         $entry->delete();
         ilCalendarCategoryAssignments::_deleteByAppointmentId($entry_id);
     }
     ilBookingEntry::removeObsoleteEntries();
     ilUtil::sendSuccess($this->lng->txt('cal_deleted_app'), true);
     $this->ctrl->redirect($this, 'appointmentList');
 }