mod_http_oauth2: Fill in some client metadata defaults Explicit > Implicit Maybe we should actually use these for something as well? :) It's is somewhat an open question of how strictly we should enforce things in the client metadata given that it is somewhat extensible. Especially some of these enum fields which have corresponding IANA registries.

This module helps make BOSH and WebSocket connection endpoints
discoverable via the HTTP method described in
[XEP-0156](https://xmpp.org/extensions/xep-0156.html#http).