mod_pubsub_serverinfo: Detect existence of pub/sub node Instead of blindly trying to create the pub/sub node to publish items to, a service discovery query is performed to check if node creation is required. Added various bits of warn and debug logging, to give a user better feedback if and why something is failing.

mod_pubsub_serverinfo: implemented all basic features This commit replaces the earlier proof-of-concept to a solution that: - reports on remotely-connected domains - uses disco/info to detect if those domains opt-in - publishes domain names for remote domains that do so - caches the disco/info response

mod_csi_battery_saver: mark some presences as important

mod_pubsub_serverinfo: New module that uses pub/sub to make accessible server info This first implemetnation is laughably simple: it only adds a disco#info feature. This flags 'opt-in' for inclusion of local domain names in the data exposed by other domains (per the domain), which will allow servers to be listed in the XMPP Network Graph at https://xmppnetwork.goodbytes.im Hopefully, this bare-boned implementation acts as a stepping stone for future improvements.

mod_groups_internal: Set group names as roster groups

mod_http_oauth2: Reduce log level for error delivery via redirect This is supposed to be normal in OAuth2, not really deserving a warning log message.

mod_http_oauth2: Tweak fallback error text Since the oauth error is more like the error condition, a symbolic error code, not the most human-friendly. Many error cases do have human-readable error descriptions that should be fine on their own, or changed to be. As a fallback, capitalize the error name.

mod_http_oauth2: Improve registration schema documentation parts

mod_http_oauth2: Do not enforce PKCE on Device and OOB flows PKCE does not appear to be used with the Device flow. I have found no mention of any interaction between those standards. Since no data is delivered via redirects in these cases, PKCE may not serve any purpose. This is mostly a problem because we reuse the authorization code to implement the Device and OOB flows.

mod_groups_internal: Return group name instead of MUC name if MUC has no name