code: protected function addProductField(FormBuilderInterface $builder)
      {
          $builder->add(static::FIELD_PRODUCT, HiddenType::class, [
              'required' => true,
              'constraints' => [
                  new NotBlank(),
              ],
          ]);
  
          return $this;
      }
docs: @param \Symfony\Component\Form\FormBuilderInterface $builder
  
  @return $this