Add and consume multi-lookup API endpoint

osu.Game/Online/API/Requests/GetUsersResponse.cs

@@ -0,0 +1,15 @@
+// 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.Collections.Generic;
+using Newtonsoft.Json;
+using osu.Game.Users;
+
+namespace osu.Game.Online.API.Requests
+{
+    public class GetUsersResponse : ResponseWithCursor
+    {
+        [JsonProperty("users")]
+        public List<User> Users;
+    }
+}