code: protected function addEmailField(FormBuilderInterface $builder)
      {
          $builder->add(self::FIELD_EMAIL, EmailType::class, [
              'label' => 'availability_alert.submit.email',
              'required' => true,
              'constraints' => [
                  new NotBlank(),
              ],
          ]);
  
          return $this;
      }
docs: @param \Symfony\Component\Form\FormBuilderInterface $builder
  
  @return $this