code: func (ingressStrategy) ValidateUpdate(ctx context.Context, obj, old runtime.Object) field.ErrorList {
  	validationErrorList := validation.ValidateIngress(obj.(*networking.Ingress))
  	updateErrorList := validation.ValidateIngressUpdate(obj.(*networking.Ingress), old.(*networking.Ingress))
  	return append(validationErrorList, updateErrorList...)
  }
docs: // ValidateUpdate is the default update validation for an end user.