fix: #9127, scope service worker to relative_path for the forum (#9239)

Adds a `Service-Worker-Allowed` header on `assets/src/service-worker.js` URL and uses `scope` option during registration to ensure the service worker is correctly scoped to the entire forum and only the forum.

public/src/app.js

@@ -788,7 +788,7 @@ app.cacheBuster = null;
 
 	function registerServiceWorker() {
 		if ('serviceWorker' in navigator) {
-			navigator.serviceWorker.register(config.relative_path + '/assets/src/service-worker.js')
+			navigator.serviceWorker.register(config.relative_path + '/assets/src/service-worker.js', { scope: config.relative_path + '/' })
 				.then(function () {
 					console.info('ServiceWorker registration succeeded.');
 				}).catch(function (err) {

src/routes/meta.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const path = require('path');
+const nconf = require('nconf');
 
 module.exports = function (app, middleware, controllers) {
 	app.get('/sitemap.xml', controllers.sitemap.render);
@@ -11,7 +12,7 @@ module.exports = function (app, middleware, controllers) {
 	app.get('/manifest.webmanifest', controllers.manifest);
 	app.get('/css/previews/:theme', controllers.admin.themes.get);
 	app.get('/osd.xml', controllers.osd.handle);
-	app.get('/service-worker.js', function (req, res) {
-		res.status(200).type('application/javascript').sendFile(path.join(__dirname, '../../public/src/service-worker.js'));
+	app.get('/assets/src/service-worker.js', function (req, res) {
+		res.status(200).type('application/javascript').set('Service-Worker-Allowed', nconf.get('relative_path') + '/').sendFile(path.join(__dirname, '../../public/src/service-worker.js'));
 	});
 };