Allow to manually specify a Content-Length on setBody(Publisher<ByteBuffer>)

[schmitch]

Actually when running something like that:

 new RequestBuilder().setUrl("http://localhost:9004/").setMethod("POST").setBody(publisher).setContentLength(3)

while publisher is of type Publisher<ByteBuffer> the setContentLength will be ignored?! And a Header of type Transfer-Encoding: chunked will be added. However it would be great to set that manually on Streaming bodies so if a Content-Length is there it will be used else it's the old behavior. The use case is simple, stream data where the size is known or computed and the receiving client needs to know the Content-Length.

[schmitch]

@slandelle when do you create the next Milestone?

[slandelle]

Done: 2.0.0-RC21 (sic)