/**
  * Retourne l'image principale de l'utilisateur
  * @param  FacebookSession       $session [description]
  * @param  AdvancedUserInterface $user    [description]
  * @return [type]                         [description]
  */
 public function getUserPicture(FacebookSession $session, AdvancedUserInterface $user)
 {
     if (!is_null($user->getFacebookId())) {
         $request = new FacebookRequest($session, 'GET', '/me/picture', ['redirect' => false, 'type' => 'large']);
         $response = $request->execute();
         $graphObject = $response->getGraphObject();
         return $graphObject->getProperty('url');
     }
 }