mod_http_oauth2: Validate (unused at this point) localized URIs Client registration may include keys of the form "some_uri#lang-code" pointing to alternate language versions of the various URIs. We don't use this yet but the same validation should apply.

This module writes out a traceback to `traceback.txt` in Prosodys data
directory (see `prosodyctl about`) when the signal `SIGUSR1` is
received. This is useful when debugging seemingly frozen instances in
case it is stuck in Lua code.