foo.php

<?php

public function getValidationGroupSpecification()
{
  if ($this->authorizationService->hasRole('admin')) {
    $fields[] = 'password';
  }
  
  return [
    'put' => ['first_name', 'last_name'] + $fields,
    'post' => ['first_name', 'last_name', 'password', 'credit_card']
  ]
}