mod_http_oauth2: Reflect changes to defaults etc
- Resource owner password grant was disabled by default
- Tokens now include a hash of client_id making it possible to be
reasonable sure that they were issued to a particular client
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.