docs: function signOutUser(req, res, next) {
      debug('Signing out user');
      //make a best attempt effort at revoking the tokens
      var accessToken = req.session.auth ? req.session.auth.access_token: null;
      var refreshToken = req.session.auth ? req.session.auth.refresh_token: null;
      if (accessToken) {
          debug('Revoking access token');
          request.get({
              url: LOGOUT_URL,
              qs: {
                  token: accessToken
              }
          }, function(err, response, body) {
              if (err) {
                  debug('Error revoking access token', err.message);
              } else {
                  debug('Revoked access token, %s', response.statusCode);
              }
          });
      }
  
      if (refreshToken) {
  
          request.get({
              url: LOGOUT_URL,
              qs: {
                  token: refreshToken
              }
          }, function (err, response, body) {
              if (err) {
                  debug('Error revoking refresh token', err.message);
              } else {
                  debug('Revoked refresh token, %s', response.statusCode);
              }
          });
      }
      delete req.session.auth;
      res.sendStatus(200);
  }