Enhanced proposal to NIP6: Multi-seed nostr key pairs

[ecurrencyhodler]

Using multiple seeds to generate nostr key pairs will allow nostr identities to be:

1. redundant
2. flexible

Redundant With a 2-3 keyset, a user can still retain access to their nostr identity using the other two keys to log-in if one key gets compromised.

Flexible The key set can dynamically change as long as two keys are used to rotate one out. This allows a user to easily restore their keyset and re-introduce flexibility again if a key gets compromised.

Other advantages are that bitcoiners already use an m-of-n model for their multisig wallets. That means this isn't a foreign concept and current multisig wallets could even be repurposed for their nostr identities. We don't have to reinvent the wheel for securing the seeds either as they are well-established through hardware wallets or encrypted mobile keys. And it has built-in multifactor authentication, which is doubly important when using a protocol that has no undo button.