Amend NIP-52 to include e and p tags to calendar event RSVPs

[tyiu]

This PR attempts to address two use cases with calendar event RSVPs:

1. I want a way to have my RSVP not hold true in perpetuity if I know that the calendar event I'm responding to has a chance of changing in a way that makes me not want to attend anymore.
2. The author of the calendar event being responded to may want an easy way of pulling all responses to any event that they authored in one query.

[tyiu]

@zmeyer44 @vicariousdrama @staab please review this NIP-52 calendar event RSVP amendment.

[staab]

I think we should limit this to adding optional e and a tags, since making a optional and e required isn't backwards-compatible. Adding language that clients SHOULD prefer the e tag if available basically gets us the pinning behavior you're looking for if clients start publishing e tags.

[vicariousdrama]

I concur with @staab in that I'd prefer them to be optional.

[tyiu]

@staab @vicariousdrama Updated.

[staab]

LGTM, is this implemented anywhere?

[tyiu]

LGTM, is this implemented anywhere?

No, I'll implement this now in Nostr SDK for Apple Platforms, which Comingle uses. Happy to hold off on merging until it's implemented.

[AsaiToshiya]

Won't making a optional break backward compatibility? I think the current implementations expect a to exist.

[staab]

Ah yeah, good point, that's what I originally meant

[AsaiToshiya]

If clients prioritize e, there is no need to change a.

[tyiu]

Thank you all for helping me iterate on this PR. I've pushed a commit to address your feedback.