Sadly this in a bit of state of flux. I created something called `FutureStream` which _can_ be used for this (but needs changes in asynchttpserver: the `body` should be a `FutureStream` just like `HttpClient`'s request object's `body` is also a `FutureStream`). The `FutureStream` has issues though and we plan to redesign it, see [https://github.com/nim-lang/Nim/issues/7126](https://github.com/nim-lang/Nim/issues/7126).
Any help in fixing #7126 is appreciated (by anyone).
