docs: function stormpathUserAgentMiddleware(req, res, next) {
      var newUserAgent = userAgent;
      var config = req.app.get('stormpathConfig');
      var stormpathAgent = req.headers['x-stormpath-agent'];
  
      if (stormpathAgent) {
        newUserAgent = stormpathAgent + ' ' + userAgent;
      }
  
      config.userAgent = newUserAgent;
  
      next();
    }