Redirect on changed user and org name (#11649)

* Add redirect for user

* Add redirect for orgs

* Add user redirect test

* Appease linter

* Add comment to DeleteUserRedirect function

* Fix locale changes

* Fix GetUserByParams

* Fix orgAssignment

* Remove debug logging

* Add redirect prompt

* Dont Export DeleteUserRedirect & only use it within a session

* Unexport newUserRedirect

* cleanup

* Fix & Dedub API code

* Format Template

* Add Migration & rm dublicat

* Refactor: unexport newRepoRedirect() & rm dedub del exec

* if this fails we'll need to re-rename the user directory

Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

models/migrations/v167.go

@@ -0,0 +1,24 @@
+// Copyright 2021 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 migrations
+
+import (
+	"fmt"
+
+	"xorm.io/xorm"
+)
+
+func addUserRedirect(x *xorm.Engine) (err error) {
+	type UserRedirect struct {
+		ID             int64  `xorm:"pk autoincr"`
+		LowerName      string `xorm:"UNIQUE(s) INDEX NOT NULL"`
+		RedirectUserID int64
+	}
+
+	if err := x.Sync2(new(UserRedirect)); err != nil {
+		return fmt.Errorf("Sync2: %v", err)
+	}
+	return nil
+}