code: func (statefulSetStatusStrategy) PrepareForUpdate(ctx context.Context, obj, old runtime.Object) {
  	newStatefulSet := obj.(*apps.StatefulSet)
  	oldStatefulSet := old.(*apps.StatefulSet)
  	// status changes are not allowed to update spec
  	newStatefulSet.Spec = oldStatefulSet.Spec
  }
docs: // PrepareForUpdate clears fields that are not allowed to be set by end users on update of status