@Override
public DeleteControl cleanup(MultipleOwnerDependentCustomResource primary,
		Context<MultipleOwnerDependentCustomResource> context) throws Exception {
	
	logger.debug(String.format(">>> cleanup: %s", primary.getMetadata().getName()));

	if (primary != null) {

		Optional<ConfigMap> cm = getSecondaryResource(primary, context);

		cm.ifPresent(p -> {
			var data = cm.map(ConfigMap::getData).orElse(new HashMap<>());

			data.clear(); // will trigger the rebuild of the config-map with only the data that are part of the owner refs
			p.getMetadata().getOwnerReferences().remove(primary.getMetadata().getName());

			context.getClient().resource(p).update();
		});
	}

	return DeleteControl.defaultDelete();
}

public Optional<ConfigMap> getSecondaryResource(MultipleOwnerDependentCustomResource primary,
		Context<MultipleOwnerDependentCustomResource> context) {
	InformerEventSource<ConfigMap, MultipleOwnerDependentCustomResource> ies = (InformerEventSource<ConfigMap, MultipleOwnerDependentCustomResource>) context
			.eventSourceRetriever().getEventSourceFor(ConfigMap.class);
	return ies.get(
			new ResourceID(MultipleOwnerDependentConfigMap.RESOURCE_NAME, primary.getMetadata().getNamespace()));
}