This is a nodejs express project. You know the drill
npm i
to install
npm start
to start the server
Use render.com to quick spin this in one of their free tier to test.
Ever wondered how to use upi://pay deep link in google forms or Telegram or whatsapp? Actually, its impossible to write html formatted text which accepts upi deeplink url.
Create a proxy which accepts all the parameters like pa, pn, am, tn and redirects to a constructed upi deeplink url. Since this goes back to the mobile browser, it does the magic of asking which app to use or uses the default app configured for UPI.