Allow setting transfer_group identifier

[AugustMiller]

We're looking at implementing a kind of merchant system for event ticket sales, and would love to have a way of sending an initial transfer_group param for Charges. Periodically, we're going to make Transfers to event organizers (carts may contain tickets from multiple organizers), and pairing these up will make record keeping much easier—and (in theory) tie them together in the Stripe dashboard.

I appreciate the decision to ignore modifications to the Transaction object when emitting the EVENT_BUILD_GATEWAY_REQUEST, but because this is a core param (and not a metadata candidate), we don't have a way of including this.

Is that something to be accomplished with a custom event? Probably not something to do by default, but emitting EVENT_ASSIGN_TRANSFER_GROUP would be super useful!

…or, maybe there's another way to tap in to the request params, already?

❤️

[AugustMiller]

Well, if I'd kept reading, I'd have learned that we might be able to retroactively group these, when creating Transfers in Stripe… I'll continue to investigate. ✌️

[andris-sevcenko]

What's your timeline for this?

[AugustMiller]

Nothing urgent. Still in the proposal phase for the project, and doing some research! If we find ourselves at an impasse, I'm happy to issue a PR—I imagine this is a pretty infrequent use-case, and it may already be handled by the Transfer API.

Will @ you if I find out anything actionable! 😄

[andris-sevcenko]

The EVENT_BUILD_GATEWAY_REQUEST event allows for setting arbitrary parameters as of 04a1cdf

Sorry for the delayed notification :(