/**
  * @param OptionsResolverInterface $resolver
  */
 public function setDefaultOptions(OptionsResolverInterface $resolver)
 {
     $resolver->setRequired(['type']);
     $resolver->addAllowedTypes(['type' => ['string']]);
     $resolver->setAllowedValues(['type' => Participant::getAllTypes()]);
     $resolver->setDefaults(['data_class' => Participant::class]);
 }