Extract update into PreUpdate(), add test

osu.Game/Database/ArchiveModelManager.cs

@@ -430,10 +430,20 @@ namespace osu.Game.Database
             {
                 item.Hash = computeHash(item);
 
+                PreUpdate(item);
+
                 ModelStore.Update(item);
             }
         }
 
+        /// <summary>
+        /// Perform any final actions before the update to database executes.
+        /// </summary>
+        /// <param name="item">The <typeparamref name="TModel"/> that is being updated.</param>
+        protected virtual void PreUpdate(TModel item)
+        {
+        }
+
         /// <summary>
         /// Delete an item from the manager.
         /// Is a no-op for already deleted items.