Merge pull request #2090 from stripe/remi-add-inevent-voicepaid

Add support for `invoice.paid` event

Author: remi-stripe

src/Stripe.net/Constants/Events.cs

@@ -321,6 +321,12 @@ public static class Events
         /// </summary>
         public const string InvoiceMarkedUncollectible = "invoice.marked_uncollectible";
 
+        /// <summary>
+        /// Occurs whenever an invoice payment attempt succeeds or an invoice is marked as paid
+        /// out-of-band.
+        /// </summary>
+        public const string InvoicePaid = "invoice.paid";
+
         /// <summary>
         /// Occurs whenever an invoice payment attempt requires further user action to complete.
         /// </summary>