Move issues related files into models/issues (#19931)

* Move access and repo permission to models/perm/access

* fix test

* fix git test

* Move functions sequence

* Some improvements per @KN4CK3R and @delvh

* Move issues related code to models/issues

* Move some issues related sub package

* Merge

* Fix test

* Fix test

* Fix test

* Fix test

* Rename some files

models/db/consistency.go

@@ -0,0 +1,27 @@
+// Copyright 2022 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 db
+
+import "xorm.io/builder"
+
+// CountOrphanedObjects count subjects with have no existing refobject anymore
+func CountOrphanedObjects(subject, refobject, joinCond string) (int64, error) {
+	return GetEngine(DefaultContext).Table("`"+subject+"`").
+		Join("LEFT", "`"+refobject+"`", joinCond).
+		Where(builder.IsNull{"`" + refobject + "`.id"}).
+		Select("COUNT(`" + subject + "`.`id`)").
+		Count()
+}
+
+// DeleteOrphanedObjects delete subjects with have no existing refobject anymore
+func DeleteOrphanedObjects(subject, refobject, joinCond string) error {
+	subQuery := builder.Select("`"+subject+"`.id").
+		From("`"+subject+"`").
+		Join("LEFT", "`"+refobject+"`", joinCond).
+		Where(builder.IsNull{"`" + refobject + "`.id"})
+	b := builder.Delete(builder.In("id", subQuery)).From("`" + subject + "`")
+	_, err := GetEngine(DefaultContext).Exec(b)
+	return err
+}