Had a productive couple of days rewriting the Cashu Spilman Channel code, and the corresponding NUT

The proposed protocol was updated a week ago, and I've updated the code. Main coding challenge was to get the fee-handling exactly right.

Code still kinda messy, but all the functionality is right. And I've been gradually adding more automated tests and tidying it up.

I'll update properly another time, with more links and maybe a proper demo video, but I'm just sharing this because I should post on Nostr more often 😀

https://github.com/cashubtc/nuts/pull/296/files