private function checkRegistrationAccessToken(Request $request, Client $client)
 {
     $raw = $request->get('access_token', $request->headers->get('authorization'));
     $token = str_replace('Bearer ', '', $raw);
     $metadata = $client->getMetadata();
     if (!$token || $metadata->getRegistrationAccessToken() !== $token) {
         throw $this->createAccessDeniedException();
     }
 }