mod_http_oauth2: Improve handling of redirect_uri matching and fallback Per OAuth 2.1, the client MUST provide a redirect_uri explicitly if it registered multiple. If it only registered a single URI, it may be omitted from the authorize request.

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.