code: function callbackMiddleware (req, res, next) {
    if (req.url.indexOf('callback') === -1) {
      next()
    } else if (req.url.indexOf('error') === -1) {
      res.status(200).jsonp({ created: true })
    } else {
      res.status(400).jsonp({ error: true })
    }
  }
docs: Respond 400 {error: true} when url contains callback and error Respond 200 {created: true} when url contains callback without error