Switch from System.Text.Json to Newtonsoft, typify the BTCPayServer.Client

BTCPayServer.Client/Serializer.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using BTCPayServer.Client.JsonConverters;
+using Newtonsoft.Json;
+
+namespace BTCPayServer.Client
+{
+    public class Serializer
+    {
+        public static void RegisterConverters(JsonSerializerSettings settings)
+        {
+            if (settings == null)
+                throw new ArgumentNullException(nameof(settings));
+            settings.Converters.Add(new PermissionJsonConverter());
+        }
+    }
+}