Validate migration files (#18203)

JSON Schema validation for data used by Gitea during migrations

Discussion at https://forum.forgefriends.org/t/common-json-schema-for-repository-information/563

Co-authored-by: Loïc Dachary <loic@dachary.org>

modules/migration/schemas_static.go

@@ -0,0 +1,17 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+//go:build bindata
+// +build bindata
+
+package migration
+
+import (
+	"io"
+	"path"
+)
+
+func openSchema(filename string) (io.ReadCloser, error) {
+	return Assets.Open(path.Base(filename))
+}