Invoices has events recorded

BTCPayServer/Data/InvoiceEventData.cs

@@ -0,0 +1,22 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+
+namespace BTCPayServer.Data
+{
+    public class InvoiceEventData
+    {
+        public string InvoiceDataId
+        {
+            get; set;
+        }
+        public string UniqueId { get; internal set; }
+        public DateTimeOffset Timestamp
+        {
+            get; set;
+        }
+
+        public string Message { get; set; }
+    }
+}