Description
Sending empty files in a multipart POST form is a proper use case due to web browsers supporting it.

I worked on a API layer using guzzle that had to work with an existing legacy codebase and trigger some actions (a proxy of some sort). There was a case where files had to be sent with empty content and would not work if you would omit them.

Example
_Currently no implem

Currently websockets are unsupported:

class SttpBackendStub[F[_], S] private (
    monad: MonadError[F],
    matchers: PartialFunction[Request[_, _], F[Response[_]]],
    fallback: Option[SttpBackend[F, S, NothingT]]
) extends SttpBackend[F, S, NothingT] { // TODO

(note the TODO for the NothingT type parameter which specifies what kind of websockets are supported).

The bac

The readme on Promise part is not proper. Actually, the project uses any-promise while not register bluebird. So people should be told to register their promise, otherwise the native promise would be used.