public void Register(RegistrationData registrationData)
        {
            // Registration logic

            foreach(var notifier in _notifiers)
                notifier.Notify(registrationData);
        }
        public void Register(RegistrationData registrationData)
        {
            Client client = _clientRepository.Get(registrationData.ClientId);

            // Registration logic

            _notifier.Notify(registrationData);
        }