message: add subtype

for ignoring thread_broadcast or message_changed events

Author: johnkors

Samples/HelloWorld/Program.cs

@@ -80,6 +80,9 @@ public Task<EventHandledResponse> Handle(EventMetaData eventMetadata, MessageEve
     {
         var str = JsonSerializer.Serialize(@event);
         Console.WriteLine(str);
+
+        var str2 = JsonSerializer.Serialize(eventMetadata);
+        Console.WriteLine(str2);
         return Task.FromResult(new EventHandledResponse("OK"));
     }
 }

source/src/Slackbot.Net.Endpoints/Models/Events/MessageEvent.cs

@@ -9,9 +9,10 @@ public class MessageEvent : SlackEvent
     public string Event_Ts { get; set; }
     public string Thread_Ts { get; set; }
     public string Channel_Type { get; set; }
+    public string SubType { get; set; }
 
     public string? Bot_id { get; set; }
-    public BotProfile Bot_Profile { get; set; }
+    public BotProfile? Bot_Profile { get; set; }
 }
 
 public class BotProfile