Add GPL modules

MediaBrowser.Controller/Providers/ICustomMetadataProvider.cs

@@ -0,0 +1,24 @@
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Library;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MediaBrowser.Controller.Providers
+{
+    public interface ICustomMetadataProvider : IMetadataProvider
+    {
+    }
+
+    public interface ICustomMetadataProvider<TItemType> : IMetadataProvider<TItemType>, ICustomMetadataProvider
+        where TItemType : BaseItem
+    {
+        /// <summary>
+        /// Fetches the asynchronous.
+        /// </summary>
+        /// <param name="item">The item.</param>
+        /// <param name="options">The options.</param>
+        /// <param name="cancellationToken">The cancellation token.</param>
+        /// <returns>Task{ItemUpdateType}.</returns>
+        Task<ItemUpdateType> FetchAsync(TItemType item, MetadataRefreshOptions options, CancellationToken cancellationToken);
+    }
+}