public async void SaveButton()
        {
            var customerFormValidator = new CustomerFormValidator();
            var validationResult      = customerFormValidator.Validate(NewCustomer);

            // For testing
            CustomerValidationResult = validationResult.IsValid;

            if (validationResult.IsValid)
            {
                var customerEntity = NewCustomer.ConvertToCustomerEntity();
                var resultTask     = await _customers.AddCustomer(customerEntity);

                // For testing
                CustomerAddResult = resultTask;

                if (resultTask)
                {
                    ClearFields();
                    await LoadCustomers();
                }
                else
                {
                    MessageBox.Show("Wystąpił błąd podczas zapisu danych. Spróbuj ponownie");
                }
            }
            else
            {
                MessageBox.Show("Błąd walidacji danych.");
            }
        }
        public async void SaveButton()
        {
            var customerModel = new CustomerModel()
            {
                Name    = CustomerName,
                Address = CustomerAddress,
                City    = CustomerCity
            };

            var customerFormValidator = new CustomerFormValidator();
            var validationResult      = customerFormValidator.Validate(customerModel);

            // For testing
            CustomerValidationResult = validationResult.IsValid;

            if (validationResult.IsValid)
            {
                var customerEntity = customerModel.ConvertToCustomerEntity();
                customerEntity.Id = customerId;

                var resultTask = await _customers.UpdateCustomer(customerEntity);

                // For testing
                CustomerUpdateResult = resultTask;

                if (resultTask)
                {
                    _events.PublishOnUIThread(new CustomerCredentialsChangedEvent());
                    this.TryClose();
                }
                else
                {
                    MessageBox.Show("Błąd podczas zapisu danych. Spróbuj ponownie");
                }
            }
            else
            {
                MessageBox.Show("Błąd walidacji danych");
            }
        }