fix: attach remaining non-enumerables to req

[kamilogorek]

Ref: #375

An issue here is that Koa wraps request object, and those properties are not enumerable – https://github.com/koajs/koa/blob/master/docs/api/request.md

bodyparser middleware, attaches body to this.request object, not this.req, therefore we have to use former as the context for the error and we cannot just say this.request.req while calling it, eg.

Raven.captureException(err, {
  req: this.request.req,
}, (sendErr, eventId) => {
  if (sendErr) console.error('Failed to send captured exception to Sentry', err);
});

This will work, but will skip the body of a request, which we definitely don't want.

[MaxBittker]

nice that this was already abstracted 👍