Split migrations folder (#21549)

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

models/migrations/v1_8/v81.go

@@ -0,0 +1,31 @@
+// Copyright 2019 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 v1_8 // nolint
+
+import (
+	"fmt"
+
+	"xorm.io/xorm"
+	"xorm.io/xorm/schemas"
+)
+
+func ChangeU2FCounterType(x *xorm.Engine) error {
+	var err error
+
+	switch x.Dialect().URI().DBType {
+	case schemas.MYSQL:
+		_, err = x.Exec("ALTER TABLE `u2f_registration` MODIFY `counter` BIGINT")
+	case schemas.POSTGRES:
+		_, err = x.Exec("ALTER TABLE `u2f_registration` ALTER COLUMN `counter` SET DATA TYPE bigint")
+	case schemas.MSSQL:
+		_, err = x.Exec("ALTER TABLE `u2f_registration` ALTER COLUMN `counter` BIGINT")
+	}
+
+	if err != nil {
+		return fmt.Errorf("Error changing u2f_registration counter column type: %w", err)
+	}
+
+	return nil
+}