Delete of postgres resource is ignored when finalizer is used

[thoro]

Please, answer some short questions which should help us to understand your problem / question better?

• Which image of the operator are you using? e.g. ghcr.io/zalando/postgres-operator:v1.15.0
• Where do you run it - cloud or metal? Kubernetes or OpenShift? Bare Metal K8s
• Are you running Postgres Operator in production? yes
• Type of issue? Bug Report

It seems that the operator ignores changes to the DeletionTimestamp, only Spec and Annotations are compared, for Deletions DeletionTimestamp is set though, and Delete is never called, because it's actually not yet deleted:

https://github.com/zalando/postgres-operator/blob/master/pkg/controller/postgresql.go#L538