Split migrations folder (#21549)

There are too many files in `models/migrations` folder so that I split
them into sub folders.

models/migrations/base/hash.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.
+
+package base
+
+import (
+	"crypto/sha256"
+	"fmt"
+
+	"golang.org/x/crypto/pbkdf2"
+)
+
+func HashToken(token, salt string) string {
+	tempHash := pbkdf2.Key([]byte(token), []byte(salt), 10000, 50, sha256.New)
+	return fmt.Sprintf("%x", tempHash)
+}