fix: #7146 Better RTL handling on (de-)authentication

- RTL is applied (or unapplied) on login and logout depending on
  user language/guest-detected language.
- config is automatically saved into res.locals.config whenever
  loadConfig is called
- On login/logout, buildHeader is called instead of getting config
- On logout, req.uid is deleted instead of set to 0

src/middleware/header.js

@@ -44,8 +44,8 @@ module.exports = function (middleware) {
 				}, next);
 			},
 			function (results, next) {
-				res.locals.config = results.config;
-				next();
+				// Return no arguments
+				setImmediate(next);
 			},
 		], next);
 	};