Explore integration of Payjoin/PDK

[moneyball]

There is an opportunity to use Payjoin to make deposits into LDK Node use 1 txn instead of 2 when an on-chain txn funds a LN wallet/channel. Mutiny is doing this. We should explore it on LDK Node (probably medium priority behind LSP client, VSS, Electrum support).

[tnull]

Yeah, I agree that, while not being an immediate priority, it would be a nice-to-have in the future. This would probably also depend on/go hand in hand with #178.

[DanGould]

Payjoin V2 in PDK eliminates the need for tor #178

[tnull]

Payjoin V2 in by PDK eliminates the need for tor #178

That's good to know! Is my impression correct that v2 is still work-in-progress in PDK? Or is it already useable?

[DanGould]

It's been released as a usable alpha with feature flag v2

[tnull]

It's been released as a usable alpha with feature flag v2

Great! Do you mind pointing me to some code that roughly shows how v2 integration looks like? I think I got confused before as the only reference to v2 I could find in the docs are the module-level docs here, which don't seem to indicate that it's ready/how it could be used: https://docs.rs/payjoin/latest/payjoin/v2/index.html

[DanGould]

v1 an v2 are backwards compatible so you should be able to use the instructions in send and receive modules. Receive has it's own v2 module Follow the payjoin-cli reference implementation's v2 feature codepath. The evolving mutiny-node implementation is another reference.

Once you construct send's RequestContext from the builder you can poll the directory by repeatedly calling extract_v2

The top level v2 module ought to be private in the next update.