> We actually might want to somehow require that the inner route never returns anything but a 2xx response.

Could this be done like so:
```scala
ctx.withRouteResponseHandling {
  case response: HttpResponse(status, _, _, _) if status.isFailure ⇒ ctx.reject()
  case Status.Failure(e)                                           ⇒ ctx.failWith(e)
}
```
?