完成离线消息发送和上线获取离线消息

Hotfix/Chat/Handler/Inner/G2Chat_ExitRequestHandler.cs

@@ -0,0 +1,16 @@
+using Fantasy;
+using Fantasy.Async;
+using Fantasy.Network.Interface;
+
+namespace NB.Chat;
+
+public class G2Chat_ExitRequestHandler : RouteRPC<Scene, G2Chat_ExitRequest, Chat2G_ExitResponse>
+{
+    protected override async FTask Run(Scene scene, G2Chat_ExitRequest request, Chat2G_ExitResponse response,
+        Action reply)
+    {
+        // 在缓存中检查该账号是否存在
+        var chatUnitManageComponent = scene.GetComponent<ChatUnitManageComponent>();
+        await chatUnitManageComponent.Offline(scene, request.AccountId, request.GateRouteId);
+    }
+}