deploy/ha documents PostgreSQL under Patroni with a three-member etcd, as
running on the reference cluster, and the address that follows the primary.
Backups read such an address as libpq host and port lists and prefer a
standby, rather than resolving the list as one name.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
