Based on the ticket I created:
#1016

I implemented this integration of Apache HttpClient 5.1 for Scribe. My code is more or less a copy of the existing HttpClient 4.x implementation (https://github.com/scribejava/scribejava/tree/master/scribejava-httpclient-apache) with the necessary modifications to dependencies and the package structure that changed with httpclient5.

What I am not 100% sure about, is the whole asynchronous stuff from HttpClient as I primarily have experience with the synchronous API. The whole asynchronous API in HttpClient 5 doesn't seem to be using the same approach anymore as before with the HttpResponse containing also the HttpEntity/InputStream. But there are some compatibilty classes available, so that's why I choose to stay as close to the previous implementation as possible, especially since the Scribe API primarily is using InputStream.

I used and tested the same implementation also in our project, but as I just implemented it, I don't yet have any experience over a longer period of usage.