We currently have:

• ConnectionStrategy#keepAlive that takes a HttpRequest and a HttpResponse so it doesn't know anything about the body
• NettyResponseBodyPart#closeConnection: ugly as it's a mutable field, and that's aware of the HttpResponse and the body parts, but not the request

We could have a cleaner solution:

• a Handler can be aware of the HttpRequest if it extends AsyncHandlerExtensions
• instead of using a mutable field, we could add new States: ABORT_AND_CLOSE and CONTINUE_AND_CLOSE

@jfarcand WDYT?