fix(stripe): correcting webhook

backend/Modules/Tipping/Handlers/SendTip.cs

@@ -13,12 +13,12 @@ internal static class SendTip
         decimal Amount,
         string Currency,
         string Message,
-        string CheckoutSuccessUrl,
-        string CheckoutCancelledUrl);
+        Uri CheckoutSuccessUrl,
+        Uri CheckoutCancelledUrl);
 
     internal record Response(
         string Id,
-        string Url);
+        Uri Url);
 
     internal class Validator : Validator<Request>
     {
@@ -116,7 +116,7 @@ internal static class SendTip
             await dbContext.SaveChangesAsync(ct).ConfigureAwait(false);
 
             await SendAsync(
-                    new Response(checkout.Id, checkout.Url),
+                    new Response(checkout.Id, new Uri(checkout.Url)),
                     cancellation: ct)
                 .ConfigureAwait(false);
         }