Split migrations folder (#21549)

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

models/migrations/v1_14/v161.go

@@ -0,0 +1,74 @@
+// Copyright 2020 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_14 //nolint
+
+import (
+	"context"
+
+	"code.gitea.io/gitea/models/migrations/base"
+
+	"xorm.io/xorm"
+)
+
+func ConvertTaskTypeToString(x *xorm.Engine) error {
+	const (
+		GOGS int = iota + 1
+		SLACK
+		GITEA
+		DISCORD
+		DINGTALK
+		TELEGRAM
+		MSTEAMS
+		FEISHU
+		MATRIX
+		WECHATWORK
+	)
+
+	hookTaskTypes := map[int]string{
+		GITEA:      "gitea",
+		GOGS:       "gogs",
+		SLACK:      "slack",
+		DISCORD:    "discord",
+		DINGTALK:   "dingtalk",
+		TELEGRAM:   "telegram",
+		MSTEAMS:    "msteams",
+		FEISHU:     "feishu",
+		MATRIX:     "matrix",
+		WECHATWORK: "wechatwork",
+	}
+
+	type HookTask struct {
+		Typ string `xorm:"VARCHAR(16) index"`
+	}
+	if err := x.Sync2(new(HookTask)); err != nil {
+		return err
+	}
+
+	// to keep the migration could be rerun
+	exist, err := x.Dialect().IsColumnExist(x.DB(), context.Background(), "hook_task", "type")
+	if err != nil {
+		return err
+	}
+	if !exist {
+		return nil
+	}
+
+	for i, s := range hookTaskTypes {
+		if _, err := x.Exec("UPDATE hook_task set typ = ? where `type`=?", s, i); err != nil {
+			return err
+		}
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+	if err := base.DropTableColumns(sess, "hook_task", "type"); err != nil {
+		return err
+	}
+
+	return sess.Commit()
+}