Separate default user into SelfhostedModule

packages/backend/src/SelfhostedModule.js

@@ -0,0 +1,12 @@
+const { AdvancedBase } = require("puter-js-common");
+
+class SelfhostedModule extends AdvancedBase {
+    async install (context) {
+        const services = context.get('services');
+
+        const DefaultUserService = require('./services/DefaultUserService');
+        services.registerService('__default-user', DefaultUserService);
+    }
+}
+
+module.exports = SelfhostedModule;