/**
  * Returns all threads with new messages
  *
  * @return array
  */
 public function threadsWithNewMessages()
 {
     $threadsWithNewMessages = [];
     $participants = Participant::where('user_id', $this->id)->lists('last_read', 'thread_id');
     if ($participants) {
         $threads = Thread::whereIn('id', array_keys($participants))->get();
         foreach ($threads as $thread) {
             if ($thread->updated_at > $participants[$thread->id]) {
                 $threadsWithNewMessages[] = $thread->id;
             }
         }
     }
     return $threadsWithNewMessages;
 }