feat(#32): Add separate flow for subscriptions

src/routes/api/subscribe/+server.ts

@@ -0,0 +1,41 @@
+import { type RequestHandler, redirect } from '@sveltejs/kit';
+import { stripe as stripeClient } from '$lib/utils/stripe';
+
+// Create a subscription checkout session
+export const POST: RequestHandler = async ({ request, cookies, locals: { safeGetSession } }) => {
+	const { session } = await safeGetSession();
+
+	if (!session) {
+		// If no session is found, the user isn't authenticated, so block the action
+		return new Response('Unauthorized', { status: 401 });
+	}
+
+	const userId = session.user.id;
+
+	// Get the price ID from the request body
+	const { priceId } = await request.json();
+
+	if (!priceId) {
+		return new Response('Price ID is required', { status: 400 });
+	}
+
+	// Create a subscription checkout session with Stripe
+	const checkoutSession = await stripeClient.checkout.sessions.create({
+		line_items: [
+			{
+				price: priceId,
+				quantity: 1
+			}
+		],
+		mode: 'subscription',
+		success_url: `${request.headers.get('origin')}/checkout/success`,
+		cancel_url: `${request.headers.get('origin')}/checkout/cancelled`,
+		metadata: {
+			userId: userId
+		}
+	});
+
+	// Store the checkout session.id for access from the frontend
+	cookies.set('checkout_session_id', checkoutSession.id, { path: '/' });
+	return redirect(303, checkoutSession.url as string);
+};