/**
  * Provides the node submission form.
  *
  * @param \Drupal\crm_core_activity\Entity\ActivityType $crm_core_activity_type
  *   The activity type to add.
  * @param \Drupal\crm_core_contact\Entity\Contact $crm_core_contact
  *   (optional) The contact the activity will be assigned. If left blank, the
  *   Form will show a field to select a contact.
  * @return array
  *   A node submission form.
  */
 public function add(ActivityType $crm_core_activity_type, Contact $crm_core_contact = NULL)
 {
     $values = array('type' => $crm_core_activity_type->id());
     if ($crm_core_contact) {
         $values['activity_participants'] = array(array('target_id' => $crm_core_contact->id()));
     }
     $activity = Activity::create($values);
     $form = $this->entityFormBuilder()->getForm($activity);
     return $form;
 }