Replace the bitnami-era pgvector:pg17 db + hand-rolled pg_upgrade entrypoint
with discourse/postgres:pg18 (pgvector + discourse's auto-upgrade layer, as
suggested on coop-cloud/discourse#16). The image does the in-place major-version
pg_upgrade itself on boot, so the recipe just configures it via env:
- cc-db-entrypoint.sh is now a 5-line wrapper that only injects the password
secret (the image reads DB_PASSWORD/POSTGRES_PASSWORD from env, no *_FILE);
- POSTGRES_USER (the install user pg_upgrade must match) defaults to the image's
'postgres' -- correct for fresh installs and bitnami-origin clusters -- and is
overridable from the app .env for a cluster bootstrapped with another superuser;
- POSTGRES_INITDB_ARGS=--no-data-checksums so the new pg18 cluster matches the
pre-18 clusters (pg18 initdb enables checksums by default, pg_upgrade requires
a match). No need to install the old postgres in our wrapper anymore.
- mount postgresql_data at /var/lib/postgresql (versioned PGDATA .../18/docker)
- pg_backup.sh: detect the superuser at runtime; fix paths for the new layout
- document POSTGRES_USER override in .env.sample and README
- bump DB_ENTRYPOINT_VERSION v7, PG_BACKUP_VERSION v3 (immutable swarm configs)
- drop entrypoint.postgres.sh.tmpl
Verified on cctest: pg17->pg18 upgrade (install user 'postgres', checksums off)
preserves data and serves over HTTPS; fresh install also works.
