code: function cors(options) {
      options = _.merge({}, DEF_CONFIG, options);
      DEBUG && debug('configure http cors middleware', options);
      return function (req, res, next) {
          if (req.headers.origin) {
              res.header('Access-Control-Allow-Origin', options.origin === '*' ? req.headers.origin : options.origin);
              res.header('Access-Control-Allow-Methods', options.methods);
              res.header('Access-Control-Allow-Headers', options.headers);
              res.header('Access-Control-Allow-Credentials', options.credentials);
              res.header('Access-Control-Max-Age', options.maxAge);
              if ('OPTIONS' === req.method) {
                  // CORS pre-flight request -> no content
                  return res.send(errors.StatusCode.NO_CONTENT);
              }
          }
          return next();
      };
  }
docs: CORS middleware.
  
  @param {*} options
  @param {String} [options.origin='*']
  @param {String} [options.methods]
  @param {String} [options.headers]
  @param {String} [options.credentials=false]
  @param {String} [options.maxAge=24*60*60]
  @returns {Function} connect/express middleware function
  @see https://developer.mozilla.org/en-US/docs/HTTP/Access_control_CORS