vercel-labs/full-stack-service-previews ? reverse-engineered prompt

Build me a full stack demo app that shows how a storefront, a checkout API, and a reservations service can all live in one deployment and be reviewed together in a preview link.

I want a simple Next.js storefront where someone can pick a product and request a quote, a FastAPI checkout backend that handles the public API, and a private Go service that manages reservations behind the scenes. Please wire it so the frontend talks to the checkout API, and the checkout API talks to the Go service through a private service connection, not a public URL.

Make it easy to run locally and easy to deploy to Vercel as one project. I also want a small smoke test I can run to verify the full request flow, plus a basic preview inspector on the page so I can see what branch and commit the preview came from. Keep the data simple and in memory for now, and make the whole thing feel like a polished template I could use to review cross service changes from one URL.