code: func (csrStrategy) ValidateUpdate(ctx context.Context, obj, old runtime.Object) field.ErrorList {
  	oldCSR := old.(*certificates.CertificateSigningRequest)
  	newCSR := obj.(*certificates.CertificateSigningRequest)
  	return validation.ValidateCertificateSigningRequestUpdate(newCSR, oldCSR)
  }
docs: // ValidateUpdate is the default update validation for an end user.