Port application from Next.js to Nuxt

Nuxt is based on Vue.js and I find their building blocks to be much
neater compared to the React based Next.js.

server/api/subscribe.post.ts

@@ -0,0 +1,29 @@
+import { readFile, writeFile } from "node:fs/promises";
+
+export default defineEventHandler(async (event) => {
+	const body: { subscription: PushSubscriptionJSON } = await readBody(event);
+	let subscriptions: PushSubscriptionJSON[];
+	try {
+		subscriptions = JSON.parse(await readFile("push-subscriptions.json", "utf-8"));
+	} catch (err: any) {
+		if (err.code !== "ENOENT") {
+			throw err;
+		}
+		subscriptions = [];
+	}
+	const existingIndex = subscriptions.findIndex(sub => sub.endpoint === body.subscription.endpoint);
+	if (existingIndex !== -1) {
+		subscriptions[existingIndex] = body.subscription;
+	} else {
+		subscriptions.push(body.subscription);
+	}
+	await writeFile(
+		"push-subscriptions.json",
+		JSON.stringify(subscriptions, undefined, "\t"),
+		"utf-8"
+	);
+	if (existingIndex !== -1) {
+		return { message: "Existing subscription refreshed."};
+	}
+	return { message: "New subscription registered."};
+})