Add Allow-/Block-List for Migrate & Mirrors (#13610)

* add black list and white list support for migrating repositories

* fix fmt

* fix lint

* fix vendor

* fix modules.txt

* clean diff

* specify log message

* use blocklist/allowlist

* allways use lowercase to match url

* Apply allow/block

* Settings: use existing "migrations" section

* convert domains lower case

* dont store unused value

* Block private addresses for migration by default

* fix lint

* use proposed-upstream func to detect private IP addr

* a nit

* add own error for blocked migration, add tests, imprufe api

* fix test

* fix-if-localhost-is-ipv4

* rename error & error message

* rename setting options

* Apply suggestions from code review

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: zeripath <art27@cantab.net>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

routers/api/v1/repo/migrate.go

@@ -212,6 +212,8 @@ func handleMigrateError(ctx *context.APIContext, repoOwner *models.User, remoteA
 		ctx.Error(http.StatusUnprocessableEntity, "", fmt.Sprintf("The username '%s' contains invalid characters.", err.(models.ErrNameCharsNotAllowed).Name))
 	case models.IsErrNamePatternNotAllowed(err):
 		ctx.Error(http.StatusUnprocessableEntity, "", fmt.Sprintf("The pattern '%s' is not allowed in a username.", err.(models.ErrNamePatternNotAllowed).Pattern))
+	case models.IsErrMigrationNotAllowed(err):
+		ctx.Error(http.StatusUnprocessableEntity, "", err)
 	default:
 		err = util.URLSanitizedError(err, remoteAddr)
 		if strings.Contains(err.Error(), "Authentication failed") ||