Documentation on Handlers returning Promises

[RatchetS2]

Many function handlers expect us to return either nothing or a Promise:
(res: HttpResponse, req: HttpRequest) => void | Promise<void>
This applies to various handlers, including HTTP method handlers, App listen/filter, and WebSocket upgrade/open/message/dropped.

Should we return a Promise that resolves once we've responded to the client?
Does it perform any cleanup or optimization with that Promise?
If its just to indicate that we can respond asynchronously, I believe it may be misleading, and we should change the signature to:
(res: HttpResponse, req: HttpRequest) => void

[uNetworkingAB]

Should we return a Promise that resolves once we've responded to the client?

No

Does it perform any cleanup or optimization with that Promise?

No

If its just to indicate that we can respond asynchronously,

Yes

I believe it may be misleading, and we should change the signature to:
(res: HttpResponse, req: HttpRequest) => void

No, that's not right. async function seemingly returning void actually returns Promise<void> so we need to accept both signatures

[RatchetS2]

I see, thats some strict TypeScript config.
I thought () => void would also allow () => Promise<void>.
But it seems that isn’t the case.