Add helpers for BIP21/Unified QR Support

[tnull]

While we probably shouldn't add dependencies for generating the actual QR codes, we should add helper methods that make it trivial to generate and parse the raw BIP21 data so that integration with any (native) QR code scanning/generation logic can easily be integrated.

Also see:
https://bitcoinqr.dev/
https://github.com/bitcoin/bips/blob/master/bip-0021.mediawiki

[bennyhodl]

What is the best way to go about this? Should this be a trait for onchain addresses and lightning invoice structs to implement?

As well as an impl function in Node to create a BIP21 invoice?

[tnull]

What is the best way to go about this? Should this be a trait for onchain addresses and lightning invoice structs to implement?

I'm not quite sure why you think this would require an extra trait?

As well as an impl function in Node to create a BIP21 invoice?

Yes I think it would mainly be a util method (probably not even on Node itself) that would take an invoice and an onchain address and spit out a bytes array/hex string that you'd only need to give to a QR code library.

We might want to use https://github.com/Kixunil/bip21 for this. However, I'm just now seeing that they upgraded to rust-bitcoin 0.30, which we can't do yet until lightningdevkit/rust-lightning#2124 lands upstream. So I'm afraid this is currently blocked on this :/

[jbesraa]

I understand the reasoning behind not adding a new dep for this, but it would be nice to actually have some standard around different projects. at payjoin we are using https://github.com/Kixunil/bip21 and planning to maintain it

[tnull]

I understand the reasoning behind not adding a new dep for this, but it would be nice to actually have some standard around different projects. at payjoin we are using https://github.com/Kixunil/bip21 and planning to maintain it

No, I wasn't saying we don't want to add the dependency. Rather, we can't currently as we still run an incompatible version of rust-bitcoin. This will be unblocked by #214.

[DanGould]

Seems like this has been unblocked