Re: [webpayments] How can the API support enrollment (future payment) use cases? (#65)

To support enrollment in a service or a future charge, I propose that the `details` object can contain `"is_billing_agreement": true` key-value pair.

- For periodic billing: the `amount` should be the estimated periodic charge amount.
- For future charge: the `amount` should be the estimated future charge.

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/webpayments/issues/65#issuecomment-182134027