An xpub is all that is needed for payments on the chain. You can export hundreds of address upfront, and so you have your basic raw API at hand in a text file.
The problem is integrating it smoothly with the user billing system. Perhaps you can use something like https://books.libreoffice.org/en/WG71/WG7114-MailMerge.html for a basic automation (but you miss the qrcode goodie).
For LN you can use some service like LNbits, I suppose there are several that expose an API, along with a GUI for the invoicing system.