Set OwnerReference of Clusters to Tenant

[srueg]

Set an ownerReference on newly created clusters to the respective tenant object.

Just as we do for GitRepo objects.

The result is that cluster objects will then automatically be deleted if the owner (tenant) is deleted. This can be good or bad, maybe an opt-out mechanism (i.e. annotation) needs to be available?

[tobru]

What about a finalizer on the Tenant which blocks deletion until all references are gone?

[srueg]

That is done automatically with ownerReferences. If you delete an owner with delete propagation "foreground" it adds a finalizer which is only removed once all owner objects are deleted.