[Feature Request] Payjoin v2 support

[Sami32]

https://payjoin.org/docs/how-it-works/payjoin-v2-bip-77/
https://github.com/payjoin

https://en.bitcoin.it/wiki/PayJoin_adoption
Payjoin Roadmap 📝 (view)

[andreasgriffin]

Once its in bdk, I'l consider adding it.

[DanGould]

We've got examples with bdk but I don't know that it'll ever make sense to be "in" bdk since bdk manages keys and syncing payjoin manipulates PSBTs and network messages. They work really nicely together in Bull Bitcoin Mobile and we do have working python bindings.

Might you let me know why being "in bdk" is a threshold for bitcoin-safe?

[andreasgriffin]

Thanks for the clarification. I didn't know there are python bindings.
Payjoin is really cool and this integration test is a good starting point.

[DanGould]

That integration test plus the reference implementation will take an implementer very far

Happy to walk you through it all any time

[andreasgriffin]

I'm thinking about the fallback tx and with it's requirement to sign 2 transactions in total. For a wallet with hot seeds that can be done in the background, but for Bitcoin Safe (hardware signer only), this is a serious UX hurdle.