mod_http_oauth2: Allow omitting application type for native apps This derives "application_type":"native" from the first redirect URI when registering a client, so that it can be omitted without the default value of "web" causing the very same redirect URIs to be rejected.

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.