Add frontend support for user

frontend/src/routes/notifications/[subscription_id]/+page.ts

@@ -0,0 +1,23 @@
+import type { PageLoad } from './$types';
+import { getSubscription, fetchSubscriptionNotifications } from '$lib/api';
+
+export const load: PageLoad = async ({ params }) => {
+	if (import.meta.env.SSR) {
+		return {
+			subscription: null,
+			notifications: []
+		};
+	} else {
+		const subscription_id = params.subscription_id;
+
+		const subscription = await getSubscription(subscription_id);
+		const notifications = (await fetchSubscriptionNotifications(subscription_id)).sort(
+			(a, b) => new Date(b.created_at!).getTime() - new Date(a.created_at!).getTime()
+		);
+
+		return {
+			subscription: subscription,
+			notifications: notifications
+		};
+	}
+};