Make LDAP be able to skip local 2FA (#16954)

This PR extends #16594 to allow LDAP to be able to be set to skip local 2FA too. The technique used here would be extensible to PAM and SMTP sources.

Signed-off-by: Andrew Thornton <art27@cantab.net>

services/auth/source/ldap/assert_interface_test.go

@@ -16,6 +16,7 @@ import (
 type sourceInterface interface {
 	auth.PasswordAuthenticator
 	auth.SynchronizableSource
+	auth.LocalTwoFASkipper
 	models.SSHKeyProvider
 	models.LoginConfig
 	models.SkipVerifiable