public function getGoogleAuth(Request $request)
 {
     $client = new Google_Client();
     $client->setScopes(SCOPES);
     $client->setAuthConfigFile(CLIENT_SECRET_PATH);
     $client->setRedirectUri('http://' . $_SERVER['HTTP_HOST'] . '/google_calendar_callback');
     $authCode = $request->input('code');
     $accessToken = $client->authenticate($authCode);
     $client->setAccessToken($accessToken);
     $request->session()->put('access_token', $client->getAccessToken());
     $authObj = json_decode($accessToken);
     if (isset($authObj->refresh_token)) {
         $session = Session::firstOrNew($request->session()->getId());
         $session->refresh_token = $authObj->refresh_token;
         $session->save();
     }
     // Refresh the token if it's expired.
     if ($client->isAccessTokenExpired()) {
         $client->refreshToken(Session::find($request->session()->getId()));
     }
     return redirect()->route('calendar_back', [$request->session()->get('dialog'), $request->session()->get('seance')], 302);
 }