Fixed Duplicate returns on grouping

Fixed UserDataKey not stored

Jellyfin.Data/Entities/UserData.cs

@@ -8,6 +8,12 @@ namespace Jellyfin.Data.Entities;
 /// </summary>
 public class UserData
 {
+    /// <summary>
+    /// Gets or sets the custom data key.
+    /// </summary>
+    /// <value>The rating.</value>
+    public required string CustomDataKey { get; set; }
+
     /// <summary>
     /// Gets or sets the users 0-10 rating.
     /// </summary>