Add migration to reset and repopulate existing skin hashes

osu.Game/Migrations/20211020081609_ResetSkinHashes.cs

@@ -0,0 +1,23 @@
+// 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 Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using osu.Game.Database;
+
+namespace osu.Game.Migrations
+{
+    [DbContext(typeof(OsuDbContext))]
+    [Migration("20211020081609_ResetSkinHashes")]
+    public partial class ResetSkinHashes : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.Sql($"UPDATE SkinInfo SET Hash = null");
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+        }
+    }
+}