In this guide, we will add a user login and an in-app purchase (IAP) button to a web product (basic HTML file). We will do this using a couple of w3c web components from https://pay2my.app: FOSS, some HTML, and some JavaScript. We'll do this without a back-end, and then iteratively add the optional — but selectively valuable — back-end (sample Node.js).
The word "liberating" in the title of this tutorial is somewhat overloaded, on purpose: