How to send structured email markup using Gmail API and Javascript?

Question

I\'m trying to build a Javascript app that uses Gmail\'s API to send emails (to myself) including the structured data needed for Gmail\'s Inbox to recognise a hotel reservation.

Answer 1

In the end I found it was quite simple to implement a reasonably polished front-end form using client-side JavaScript and Bootstrap styling in a Google Apps Script (GAS) web app. Server-side functions handle sending the email with the structured data embedded. As GAS's MailApp.sendEmail() function digitally signs emails, this was successful. I've put the resulting code on GitHub and published the web app here. Thanks for the suggestions!