One Operator per Database

[eberlep]

To allow for database-specific Storage an Schedule/Retention options, we switch to a dedicated operator per database.

In theory, we only need to change the namespace of a newly created databae from Postgres.Spec.ProjectID to the generated database name in Postgres.ToPeripheralResourceNamespace(). This could, in theory, even be configurable.

Currently, the operator itself uses about ~35MB of ressources, the (currently not used) prometheus federation another 60MB. This is considered to be acceptable overhead.

The backup-config still remains as is, but now has to be provided when creating a new database as it can no longer be derived from the project.

[majst01]

To make this happen we need to have a Postgres.Spec.BackupID field which references to the secret which stores the backup secrets