[browser-payment-api] How are payment apps shared between different browser brands? (#38)

Migrating issue from https://github.com/w3c/webpayments/issues/15:

When a user registers a new payment instrument, how is that payment instrument shared between different browser brands? For example, if I register a Visa debit card issued by my bank in Google Chrome on my laptop, when I go to purchase something using my mobile phone, is that same debit card available to me via my Firefox web browser (assuming I've authenticated in some way with both browsers)?

There are a variety of choices here, in order of easiest to implement to hardest to implement:

1. There is no sharing mechanism
2. There is a unified payment instrument export mechanism
3. There is a storage and discovery mechanism that all browsers use to import data from other browsers

I assert that the last bullet point is what we should strive for, but we may need to take baby steps to get there. In any case, we should implement the API as if the third item existed and figure out a way to polyfill our way there.

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/browser-payment-api/issues/38