refactor: prepare to decouple the "model migration" package and "models" package (#38533)

Migrations should never use model structs directly, because the model
structs can be different in different releases. e.g. if one migration uses
"User" model, it works in the early releases, then one day, when the
User model changes, the migration breaks because it will use the
new (incorrect) User model, it should only use the old User model.

The same to "modules/structs".

---------

Signed-off-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: delvh <dev.lh@web.de>

modelmigration/v1_20/v253.go

@@ -0,0 +1,48 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_20
+
+import (
+	"gitea.dev/modelmigration/base"
+	"gitea.dev/modules/log"
+)
+
+func FixExternalTrackerAndExternalWikiAccessModeInOwnerAndAdminTeam(x base.EngineMigration) error {
+	type UnitType int
+	type AccessMode int
+
+	type TeamUnit struct {
+		ID         int64    `xorm:"pk autoincr"`
+		Type       UnitType `xorm:"UNIQUE(s)"`
+		AccessMode AccessMode
+	}
+
+	const (
+		// AccessModeRead read access
+		AccessModeRead = 1
+
+		// Unit Type
+		TypeExternalWiki    = 6
+		TypeExternalTracker = 7
+	)
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	count, err := sess.Table("team_unit").
+		Where("type IN (?, ?) AND access_mode > ?", TypeExternalWiki, TypeExternalTracker, AccessModeRead).
+		Update(&TeamUnit{
+			AccessMode: AccessModeRead,
+		})
+	if err != nil {
+		return err
+	}
+	log.Debug("Updated %d ExternalTracker and ExternalWiki access mode to belong to owner and admin", count)
+
+	return sess.Commit()
+}