Document replication slots for PG HA
repmgr can automatically manage replication slots by setting
repmgr['user_replication_slots'] = 1
They do come with risks though. Data partition can fill up with WAL logs if a standby is left down for too long.
We should document how to use these in the PG HA doc, as well as what the implications are.
We might even consider turning them on by default.
The DB instances for gitlab.com do use replication slots.