Allow null values for the Amount property in PaymentLinkRequest

src/Mollie.Api/Models/PaymentLink/Request/PaymentLinkRequest.cs

@@ -8,7 +8,7 @@ public record PaymentLinkRequest
         /// <summary>
         /// The amount that you want to charge, e.g. {"currency":"EUR", "value":"1000.00"} if you would want to charge €1000.00.
         /// </summary>
-        public required Amount Amount { get; init; }
+        public Amount? Amount { get; init; }
 
         /// <summary>
         /// This description will also be used as the payment description and will be shown to your customer on their card or bank

tests/Mollie.Tests.Integration/Api/PaymentLinkTests.cs

@@ -31,8 +31,8 @@ public async Task CanRetrievePaymentLinkList() {
 
     [DefaultRetryFact]
     public async Task CanCreatePaymentLinkAndRetrieveIt() {
-        // Given: We create a new payment
-        PaymentLinkRequest paymentLinkRequest = new PaymentLinkRequest() {
+        // Given: We create a new payment link
+        PaymentLinkRequest paymentLinkRequest = new() {
             Description = "Test",
             Amount = new Amount(Currency.EUR, 50),
             WebhookUrl = DefaultWebhookUrl,
@@ -44,7 +44,7 @@ public async Task CanCreatePaymentLinkAndRetrieveIt() {
         // When: We retrieve it
         var retrievePaymentLinkResponse = await _paymentLinkClient.GetPaymentLinkAsync(createdPaymentLinkResponse.Id);
 
-        // Then: We expect a list with a single ideal payment
+        // Then: We expect a payment link with the expected properties
         var verifyPaymentLinkResponse = new Action<PaymentLinkResponse>(response => {
             var expiresAtWithoutMs = paymentLinkRequest.ExpiresAt.Value.Truncate(TimeSpan.FromSeconds(1));
 
@@ -58,6 +58,35 @@ public async Task CanCreatePaymentLinkAndRetrieveIt() {
         verifyPaymentLinkResponse(retrievePaymentLinkResponse);
     }
 
+    [DefaultRetryFact]
+    public async Task CanCreatePaymentLinkWithNullAmount() {
+        // Given: We create a new payment link
+        PaymentLinkRequest paymentLinkRequest = new() {
+            Description = "Test",
+            Amount =  null,
+            WebhookUrl = DefaultWebhookUrl,
+            RedirectUrl = DefaultRedirectUrl,
+            ExpiresAt = DateTime.Now.AddDays(1)
+        };
+        var createdPaymentLinkResponse = await _paymentLinkClient.CreatePaymentLinkAsync(paymentLinkRequest);
+
+        // When: We retrieve it
+        var retrievePaymentLinkResponse = await _paymentLinkClient.GetPaymentLinkAsync(createdPaymentLinkResponse.Id);
+
+        // Then: We expect a payment link with the expected properties
+        var verifyPaymentLinkResponse = new Action<PaymentLinkResponse>(response => {
+            var expiresAtWithoutMs = paymentLinkRequest.ExpiresAt.Value.Truncate(TimeSpan.FromSeconds(1));
+
+            response.Amount.Should().BeNull();
+            response.ExpiresAt.Should().Be(expiresAtWithoutMs);
+            response.Description.Should().Be(paymentLinkRequest.Description);
+            response.RedirectUrl.Should().Be(paymentLinkRequest.RedirectUrl);
+        });
+
+        verifyPaymentLinkResponse(createdPaymentLinkResponse);
+        verifyPaymentLinkResponse(retrievePaymentLinkResponse);
+    }
+
     public void Dispose()
     {
         _paymentLinkClient?.Dispose();