Add finalizers to Deployment resources created by the controller to prevent clients from directly deleting them before workflow executions are properly drained. When a user attempts to delete a deployment, the finalizer ensures the controller can coordinate proper draining of that worker version before allowing the deletion.

A requested deletion should probably still trigger an immediate scale-to-zero for the deployment; scaledown is reversible however if the user chooses to remove the .metadata.deletionTimestamp marker.

https://kubernetes.io/docs/concepts/overview/working-with-objects/finalizers/