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.

Inizia con l’annotazione @ControllerConfiguration e traccia il modo in cui le implementazioni di Cleaner attivano la gestione di finalizer durante l’eliminazione di una custom resource. Conferma dove viene elaborato il delete event e come viene invocato cleanup. Il lavoro è completato quando la configurazione proposta controlla se un cleaner aggiunge un finalizer senza modificare il comportamento di cleanup e il comportamento rilevante è coperto dai test.