Returning async KakapoResponse in route handler breaks

[zzarcon]

We have an issue currently in our fetchinterceptor, in where if we return a promise of a KakapoResponse it won't actually return the response body in the handler. That happens here

const response = handler(request, db);

if (response instanceof Promise) {
  //TODO: Should we handle 'requestDelay' also for async responses?
  return response.then(data => fakeResponse(data));
}

if (!(response instanceof KakapoResponse)) {
  return new Promise(resolve =>
    setTimeout(
      () => resolve(fakeResponse(response)),
      interceptor.getDelay()
    )
  );
}

const result = fakeResponse(response.body, response.headers);
return new Promise((resolve, reject) =>
  setTimeout(() => {
    if (response.error) {
      return reject(result);
    }
    return resolve(result);
  }, interceptor.getDelay())
);

After checking if the response it's a promise, we should also check if it's a KakapoResponse one, and handle it accordingly as we do:

const result = fakeResponse(response.body, response.headers);