Include payment handler information in response

We have heard use cases for merchants having information about the user's selected payment handler for a transaction, including:

• Being able to debug issues
• Security / Trust in some payment handlers

This is most useful for standardized payment methods but may also be useful for URI-identified payment methods that allow for multiple payment handlers.

The original payment handler issue is 217:
https://github.com/w3c/payment-handler/issues/217

I am not proposing this for a v1 feature. However, when we start to consider the issue we can return to a proposal to return two bits of information in the PR API response:

handlerType: {'built-in', 'web', 'native')
handlerID: {null, <origin>, <platform-specific> }

Ian

Start by reading the original payment handler issue 217 and the discussion in this issue. Consider how handlerType and handlerID would fit the Payment Request API response, including standardized and URI-identified payment methods. Done would require a decided proposal; the issue explicitly does not target a v1 implementation.