Switch from HA-Cluster to single-instance DB for gitea

Intially I had setup a high availability cluster for my gitea instance,
basically as an experiment. Though this experiement was doomed by my
effort to keep the required infrastructure small when ever possible. In
the end I struggled with constant downtimes due to memory limitations
and other sideeffects.

On the other hand I do _not_ need a highly available DB for my very
personal git-server. In the worst case I can still deconnect the whole
thing from the internet, restart it and investigate issues without
pressure.

Note though that even this little shift needed some preparation:

1. Forward the DB-port to the local machine
   `kubectl port-forward -n gitea service/gitea-postgresql-ha-pgpool 5432:5432`
2. Create valid backup of the DB
   `pg_dump --dbname=gitea --file=/app/Gitea-$(date +%Y_%m_%d_%H_%M_%S)-dump.sql -F c --host=localhost --port=5432`
3. Apply the new setup
   `ansible-playbook site.yml --tags=gitea`
4. Forward the DB-port to the local machine of the new DB
   `kubectl port-forward -n gitea service/gitea-postgresql 5432:5432`
5. Restore the DB cleanly (`-c`)
   `pg_restore -c --username=gitea --host=localhost --port=5432 -d gitea Gitea-*-dump.sql`
6. Reupload one of the SSH-Keys to restore the SSH-configuration on disk
   from DB.

roles/k8s-setup/tasks/_gitea.yml

@@ -107,12 +107,12 @@
       persistence:
         size: 15Gi
       postgresql:
-        enabled: False
+        enabled: True
         primary:
           persistence:
             size: 2Gi
       postgresql-ha:
-        enabled: True
+        enabled: False
         persistence:
           size: 2Gi
       valkey: