[NWC] Support NIP-42 (AUTH) for zap relay

[mutatrum]

I'm running ligess, for self-custodial zaps. It has a single purpose relay, only for zapping. As this has access to my LND, it enforces AUTH on incoming connections for added security. Ligess sends an NIP-42 AUTH request, but Primal doesn't answer, after which ligess times out and the zap fails. The UI shows a zap, but it's not stored, on refresh it's gone, so there is also a small issue with verification of the zap and/or error handling of NWC zaps.

The same issue existed on Nostter when they added NWC: https://github.com/SnowCait/nostter/issues/1397