NUT-11 + NUT-14: New P2PK/HTLC rules

[robwoodgate]

Closes #310

This PR codifies the new P2PK / HTLC rules agreed to bring us in line with Bitcoin HTLC contracts.

• Cashu-TS New P2PK rules and HTLC support (NUT-14)  cashu-ts#424
• Nutshell p2pk both spend paths possible after timelock nutshell#842
• CDK fix: htlc and p2pk conditions with spec update cdk#1435
• Nutmix Htlc p2pk changes lescuer97/nutmix#205

Tl;DR:
The main (locktime) pathway remains open. Either locktime or refund pathway can be used after locktime expiry.

[thesimplekid]

This looks good. It would be nice if we could add some test vectors for this and make sure the current ones we have are up to date this this change.

[robwoodgate]

This looks good. It would be nice if we could add some test vectors for this and make sure the current ones we have are up to date this this change.

Have added / tidied / checked test vectors and done some general typo/grammar fixes.

[robwoodgate]

Further to meeting today, I've added a clarifying note that Locktime/Refund multisig conditions cannot be blended.

[thesimplekid]

CDK devs confirmed it is compliant with new rules already.

Was mistake. But have pr to bring us up to date cashubtc/cdk#1435

[robwoodgate]

CDK devs confirmed it is compliant with new rules already.

Was mistake. But have pr to bring us up to date cashubtc/cdk#1435

Appreciate you taking care of it @thesimplekid

[d4rp4t]

Wouldn't be cleaner if we moved multisig test vectors under sig_inputs?

[robwoodgate]

Wouldn't be cleaner if we moved multisig test vectors under sig_inputs?

Although those tests are SIG_INPUTS, they are examples of general multisig conditions. Whether they are SIG_INPUTS or SIG_ALL doesn't change the examples.