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

% Prosody log format for lnav

This is a format definition that allows <https://lnav.org/> to better
handle Prosody logs.

Install it using `lnav -i ./prosody.json`