Как правильно сделать с точки зрения ООП и здравого смысла?

class User
{
    private $is_active = false;

    public function activate(string $activation_token) : void
    {
        if ($activation_token !== $this->getActivationToken()) {
            throw new UserActivationFailException();
        }

        $this->is_active = true;
    }

    public function getActivationToken() : string
    {
        //генерация ключа активации
    }
}

public function completeSignUpAction(Request $request) : Response
{
    $email = mb_strtolower(trim($request->get('email')), 'UTF-8');
    $activation_token = trim($request->get('token'));

    //валидация

    $entity_manager = $this->getDoctrine()->getManager();

    try {
        //ну или в контейнер можно положить
        (new UserActivator($entity_manager))->activate($email, $activation_token);

    } catch (UserActivationFailException $e) {

        throw new NotFoundHttpException();
    }

    return new RedirectResponse($this->generateUrl('login'));
}

class UserActivator
{
    private $entity_manager;

    public function __construct(EntityManager $entity_manager)
    {
        $this->entity_manager = $entity_manager;
    }

    public function activate(string $email, string $activation_token) : void
    {
        //проверка входных данных

        $user_repository = $this->entity_manager->getRepository(User::class);

        $user = $user_repository->findOneBy(['email' => $email]);

        if (is_null($user)) {
            throw new UserActivationFailException();
        }

        $user->activate($activation_token);
        $this->entity_manager->flush($user);
    }
}