Change IBeatmapMetadataInfo.Author to be an IUser

osu.Game/Beatmaps/IBeatmapMetadataInfo.cs

@@ -2,6 +2,7 @@
 // See the LICENCE file in the repository root for full licence text.
 
 using System;
+using osu.Game.Users;
 
 #nullable enable
 
@@ -35,7 +36,7 @@ namespace osu.Game.Beatmaps
         /// <summary>
         /// The author of this beatmap.
         /// </summary>
-        string Author { get; } // eventually should be linked to a persisted User.
+        IUser Author { get; }
 
         /// <summary>
         /// The source of this beatmap.