Update to ureq 3.x

### Description

DISCLAIMER: I'm the creator of ureq.

ureq 3.x has been out for about 4 months. The 2.x branch is end-of-the-line (We will do important security updates). The new version is much better structured and I consider a more solid foundation going forward.

I suggest we update from 2.x to 3.x (PR incoming).