Corner Case: Clenup Processing for Delete Event Without Finalizer

If Cleaner interface is implemented by a reconciler a finalizer is automatically added to the custom resource, and cleaner is called before it gets removed.
There is however a corner case when it makes sense to do cleanup event finalizer is not used. In case there is an in memory data held for a custom resource, so when a custom resource deleted, related indexed or in memory objects needs to be cleaned up. In this case a finalizer is not needed, since if the operator is down and the delete event is missed it's not a problem, since the cleanup is just for in memory data.

To support this we could add a feature flag to @ControllerConfiguration to don't add finalizer for cleanup: addFinalizerForCleaner.

Note that this is not a priority issue, we should probably implement it only if some requests it. Also having a finalizer in those cases would not be a big issues.

Beginne mit der Annotation @ControllerConfiguration und verfolge, wie Cleaner-Implementierungen während der Löschung einer Custom Resource die Verarbeitung von finalizer auslösen. Bestätige, wo das delete event verarbeitet wird und wie cleanup aufgerufen wird. Als abgeschlossen gilt die Arbeit, wenn die vorgeschlagene Konfiguration steuert, ob ein Cleaner einen finalizer hinzufügt, ohne das cleanup-Verhalten zu ändern, und das relevante Verhalten durch Tests abgedeckt ist.