I'd hate to have to support all three of that at launch so I'll just like to Clover's. Clover's tokenization docs are https://docs.clover.com/dev/docs/create-a-card-token but you don't want to touch the cc number/PAN so as to avoid PCI, so the flow I imagine is you charge the customers card on the POS device, then use their API to retrieve the charge https://docs.clover.com/dev/reference/getorders which includes the charge and customer id, and store that.