Symfony Form CollectionType与新/现有实体的API帖子

构建一个内部API端点，该端点允许另一个服务更新用户的特定字段，这些字段由电子邮件地址标识。如果用户不存在，则需要创建。

如果只提交新用户，代码工作得很好。

这是对API端点的POST请求。

[
    {
        "email":"existing@user.com",
        "favouriteFood": "pizza"
    },
    {
        "email":"new@user.com",
        "favouriteFood": "sweets"
    }
]

public function postUsersAction(Request $request)
{
    $form = $this->createForm(UserCollectionType::class);
    $form->submit(['users' => json_decode($request->getContent(), true)], true);
    if (!$form->isValid()) {
        return $form;
    }
    /** @var User $user */
    foreach ($form->getData()['users'] as $user) {
        $this->userManager->updateUser($user);
    }
    $this->em->flush();
    return $form->getData()['users'];
}

UserCollectionType

class UserCollectionType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('users', 'collection', [
            'allow_add' => true,
            'by_reference' => false,
            'type' => UserType::class
        ]);
    }
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'csrf_protection' => false,
            'cascade_validation' => true
        ]);
    }
    public function getBlockPrefix()
    {
        return '';
    }
}

UserType

class UserType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('email')
            ->add('favouriteFood', TextType::class);
    }
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'data_class' => User::class,
            'validation_groups' => ['user_api'],
            'cascade_validation' => true
        ]);
    }
} 

我如何更新上面的代码，使它首先检查用户是否存在，否则继续创建一个新的用户，它当前的工作方式。

我假定可以使用datattransformer，但不知道具体如何使用。

EDIT: ShylockTheCamel提出的解决方案

控制器内部。

$post = json_decode($request->getContent(), true);
$users = [];
foreach ($post as $userRaw) {
    $user = $this->em->findOneBy($userRaw['email']); // example search logic in the DB
    if (!$user) {
        $user = new User();
    }
    $users[] = $user;
}
$form = $this->createForm(UserCollectionType::class, $users);
$form->submit(['users' => $post], true);