/**
  * {@inheritdoc}
  */
 public function startTracking(User $user, Task $task)
 {
     $tracker = $this->trackerRepository->retrieveUserTracker($user);
     if ($tracker && $tracker->getTask()->getId() === $task->getId()) {
         return;
     }
     if ($tracker) {
         // stop previous tracker
         $this->processStopTracking($tracker);
     }
     $tracker = $this->trackerFactory->create($user, $task);
     $this->trackerRepository->save($tracker);
 }