Add CNPG ScheduledBackup objects

- Each db needs this configured for data to be backed up.

e.g.

```yaml
apiVersion: postgresql.cnpg.io/v1
kind: ScheduledBackup
metadata:
  name: dronetm-prod-backup
spec:
  schedule: "0 0 0 * * *"  # At midnight every day
  backupOwnerReference: self
  cluster:
    name: dronetm-prod
```