Fix Websocket OpenApi (#9935)

* Further split inbound and outbound messages

* Fix datatype for inbound start messages

* fixes from review

MediaBrowser.Controller/Net/WebSocketMessages/OutboundWebSocketMessage.cs

@@ -1,9 +1,14 @@
+using System;
+
 namespace MediaBrowser.Controller.Net.WebSocketMessages;
 
 /// <summary>
-/// Class representing the list of outbound websocket message types.
-/// Only used in openapi generation.
+/// Outbound websocket message.
 /// </summary>
-public class OutboundWebSocketMessage : WebSocketMessage
+public class OutboundWebSocketMessage : WebSocketMessage, IOutboundWebSocketMessage
 {
+    /// <summary>
+    /// Gets or sets the message id.
+    /// </summary>
+    public Guid MessageId { get; set; }
 }