Split migrations folder (#21549)

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

models/migrations/v1_11/v106.go

@@ -0,0 +1,26 @@
+// 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_11 //nolint
+
+import (
+	"xorm.io/xorm"
+)
+
+// RepoWatchMode specifies what kind of watch the user has on a repository
+type RepoWatchMode int8
+
+// Watch is connection request for receiving repository notification.
+type Watch struct {
+	ID   int64         `xorm:"pk autoincr"`
+	Mode RepoWatchMode `xorm:"SMALLINT NOT NULL DEFAULT 1"`
+}
+
+func AddModeColumnToWatch(x *xorm.Engine) (err error) {
+	if err = x.Sync2(new(Watch)); err != nil {
+		return
+	}
+	_, err = x.Exec("UPDATE `watch` SET `mode` = 1")
+	return err
+}