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/v252.go

@@ -0,0 +1,46 @@
+// 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 FixIncorrectAdminTeamUnitAccessMode(x base.EngineMigration) error {
+	type UnitType int
+	type AccessMode int
+
+	type TeamUnit struct {
+		ID         int64    `xorm:"pk autoincr"`
+		OrgID      int64    `xorm:"INDEX"`
+		TeamID     int64    `xorm:"UNIQUE(s)"`
+		Type       UnitType `xorm:"UNIQUE(s)"`
+		AccessMode AccessMode
+	}
+
+	const (
+		// AccessModeAdmin admin access
+		AccessModeAdmin = 3
+	)
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	count, err := sess.Table("team_unit").
+		Where("team_id IN (SELECT id FROM team WHERE authorize = ?)", AccessModeAdmin).
+		Update(&TeamUnit{
+			AccessMode: AccessModeAdmin,
+		})
+	if err != nil {
+		return err
+	}
+	log.Debug("Updated %d admin team unit access mode to belong to admin instead of none", count)
+
+	return sess.Commit()
+}