Implement IPC channel for `osu://` scheme links

osu.Game/IPC/OsuSchemeLinkIPCChannel.cs

@@ -0,0 +1,49 @@
+// 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 System.Diagnostics;
+using System.Threading.Tasks;
+using osu.Framework.Platform;
+using osu.Game.Online;
+
+namespace osu.Game.IPC
+{
+    public class OsuSchemeLinkIPCChannel : IpcChannel<OsuSchemeLinkMessage>
+    {
+        private readonly ILinkHandler? linkHandler;
+
+        public OsuSchemeLinkIPCChannel(IIpcHost host, ILinkHandler? linkHandler = null)
+            : base(host)
+        {
+            this.linkHandler = linkHandler;
+
+            MessageReceived += msg =>
+            {
+                Debug.Assert(linkHandler != null);
+                linkHandler.HandleLink(msg.Link);
+                return null;
+            };
+        }
+
+        public async Task HandleLinkAsync(string url)
+        {
+            if (linkHandler == null)
+            {
+                await SendMessageAsync(new OsuSchemeLinkMessage(url)).ConfigureAwait(false);
+                return;
+            }
+
+            linkHandler.HandleLink(url);
+        }
+    }
+
+    public class OsuSchemeLinkMessage
+    {
+        public string Link { get; }
+
+        public OsuSchemeLinkMessage(string link)
+        {
+            Link = link;
+        }
+    }
+}