Add all websocket messages to generated openapi spec (#9682)

* Add all websocket messages to generated openapi spec

* Use oneOf

* JsonIgnore ServerId

* Oops

* Add discriminators

* Add WebSocketMessage container for Inbound and Outbound messages

MediaBrowser.Controller/Net/WebSocketMessage.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Text.Json.Serialization;
+using MediaBrowser.Model.Session;
+
+namespace MediaBrowser.Controller.Net;
+
+/// <summary>
+/// Websocket message without data.
+/// </summary>
+public abstract class WebSocketMessage
+{
+    /// <summary>
+    /// Gets or sets the type of the message.
+    /// TODO make this abstract and get only.
+    /// </summary>
+    public virtual SessionMessageType MessageType { get; set; }
+
+    /// <summary>
+    /// Gets or sets the message id.
+    /// </summary>
+    public Guid MessageId { get; set; }
+
+    /// <summary>
+    /// Gets or sets the server id.
+    /// </summary>
+    [JsonIgnore]
+    public string? ServerId { get; set; }
+}