/**
  * @param string $id
  * @return User|null
  */
 public function getUser($id)
 {
     $cached = $this->getCachedUserById($id);
     if ($cached) {
         return $cached;
     }
     $user = $this->userService->getUser($id);
     if ($user) {
         $this->cacheUser($user);
     }
     return $user;
 }