/**
  * @return UserId
  */
 public function userId()
 {
     if (is_null($this->userId)) {
         $this->userId = UserId::fromString($this->aggregateId());
     }
     return $this->userId;
 }
 /**
  * @return UserId
  */
 public function assigneeId()
 {
     if (is_null($this->assigneeId)) {
         $this->assigneeId = UserId::fromString($this->payload['assignee_id']);
     }
     return $this->assigneeId;
 }
 /**
  * @return UserId
  */
 public function assigneeId()
 {
     return UserId::fromString($this->payload['assignee_id']);
 }
 /**
  * @return UserId
  */
 public function userId()
 {
     return UserId::fromString($this->payload['user_id']);
 }