Update maintenance-postgres.md

docs/maintenance-postgres.md

@@ -76,12 +76,17 @@ This is because newer Postgres versions cannot start with data generated by olde
 
 Upgrades must be performed manually.
 
-**Warning: If you're using Borg Backup you probably don't want to upgrade to Postgres 15 yet as there is currently no support.**
-
 This playbook can upgrade your existing Postgres setup with the following command:
 
 	ansible-playbook -i inventory/hosts setup.yml --tags=upgrade-postgres
 
+**Warning: If you're using Borg Backup keep in mind that there is no official Postgres 15 support yet.**
+However, it is possible to use the `latest` or `14` image. Edit `roles/custom/matrix-backup-borg/defaults/main.yml` and adjust the variables accordingly.
+```bash
+matrix_backup_borg_version: "latest" # or 14
+matrix_backup_borg_supported_postgres_versions: ['12', '13', '14', '15']
+```
+
 **The old Postgres data directory is backed up** automatically, by renaming it to `/matrix/postgres/data-auto-upgrade-backup`.
 To rename to a different path, pass some extra flags to the command above, like this: `--extra-vars="postgres_auto_upgrade_backup_data_path=/another/disk/matrix-postgres-before-upgrade"`