NIP-60: add Wallet Backup Events

[DanConwayDev]

to prevent loss of funds if Wallet Event is overwritten with a new privkey

[pablof7z]

ACK. I think this is a very sane addition

[trbouma]

Why kind 375? My preference would be 7377 (which I am implementing). I think it would be a good idea to keep all the cashu wallet regular events in a 73XX block. I think event kinds <1000 should be reserved for very nostr-generic things versus more specific things, like wallets.

Also, are these backup events for kind 7375 only (i.e., proofs) or other events? If just for 7375, the example should show a proof instead.

[DanConwayDev]

Why kind 375? My preference would be 7377 (which I am implementing). I think it would be a good idea to keep all the cashu wallet regular events in a 73XX block. I think event kinds <1000 should be reserved for very nostr-generic things versus more specific things, like wallets.

Kind 375 was chosen to maintain a consistent numbering theme but I'm not precious about it. It is currently implemented in the Applesauce library, being used in experimental wallets within GitWorkshop and Nostrudel. Since 375 is only utilized for experimental wallets, I don't see any issue with transitioning to 7377.

I'll update the PR if @hzrd149 is happy and updates the applesauce.

Also, are these backup events for kind 7375 only (i.e., proofs) or other events? If just for 7375, the example should show a proof instead.

Its a backup the wallet event 17375 only and not each proof. I dont think backing up each proof at a protocol level is a good idea.