Initial draft of actor runtime abstractions (#197)

* Initial draft of actor runtime abstractions

dotnet/samples/HelloHttpApi/HelloHttpApi.ApiService/InvocationResponse.cs

@@ -0,0 +1,15 @@
+// Copyright (c) Microsoft. All rights reserved.
+
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace HelloHttpApi.ApiService;
+
+public class InvocationResponse
+{
+    [JsonPropertyName("response")]
+    public JsonElement Response { get; set; }
+
+    [JsonPropertyName("status")]
+    public string? Status { get; set; } = "success";
+}