Add models for users and rooms

osu.Game/Online/RealtimeMultiplayer/MultiplayerRoom.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using System.Collections.Generic;
 
 namespace osu.Game.Online.RealtimeMultiplayer
 {
@@ -11,5 +12,13 @@ namespace osu.Game.Online.RealtimeMultiplayer
         public long RoomID { get; set; }
 
         public MultiplayerRoomState State { get; set; }
+
+        public IReadOnlyList<MultiplayerRoomUser> Users => users;
+
+        private List<MultiplayerRoomUser> users = new List<MultiplayerRoomUser>();
+
+        public void Join(int user) => users.Add(new MultiplayerRoomUser(user));
+
+        public void Leave(int user) => users.RemoveAll(u => u.UserID == user);
     }
 }

osu.Game/Online/RealtimeMultiplayer/MultiplayerRoomUser.cs

@@ -0,0 +1,21 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+using osu.Game.Users;
+
+namespace osu.Game.Online.RealtimeMultiplayer
+{
+    public class MultiplayerRoomUser
+    {
+        public MultiplayerRoomUser(in int userId)
+        {
+            UserID = userId;
+        }
+
+        public long UserID { get; set; }
+
+        public MultiplayerUserState State { get; set; }
+
+        public User User { get; set; }
+    }
+}

osu.Game/Online/RealtimeMultiplayer/MultiplayerUserState.cs

@@ -0,0 +1,13 @@
+// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
+// See the LICENCE file in the repository root for full licence text.
+
+namespace osu.Game.Online.RealtimeMultiplayer
+{
+    public enum MultiplayerUserState
+    {
+        Watching,
+        Ready,
+        Playing,
+        Results,
+    }
+}