NIP-91: Add group channels extension to NIP-29

[Anderson-Juhasc]

No description provided.

[fiatjaf]

This looks good actually.

[Anderson-Juhasc]

Any suggestions would be great.

[staab]

I knew this would happen eventually. Flotilla already uses NIP 29 groups as channels within a larger group (the relay). So the UX this is aiming for already exists using a different approach.

My design aside, I assume the fallback UX for clients not supporting this NIP would be to simply merge all channels in a group into a single stream. I don't think that works though, because there will be confusing context depending on what type of client a user is on.

My preference would be to establish some kind of naming convention or "parent" tag for groups, so that non-supporting clients can show all groups in a flat hierarchy. Clients that do support nesting would simply show the groups differently in the navigation, as "channels".

[MerryOscar]

I like this approach 👍

One thing I would suggest is changing the channel id i tags in the kind:9 group chat messages to c tags to match the kind: 39010 channel definition.

The main reason being they conflict with NIP-73 i tags. At Fountain we are exploring NIP-29 for podcast group chat - and including i tags in chat events to reference podcast episodes is important to allow the group chat to be accessible in any podcast app in such a way that it can render episodes as native playable entities (rather than urls for a specific podcast player). I imagine this would also apply to other NIP-73 tags.

[Anderson-Juhasc]

This PR was created from master by mistake.
Replaced by #2199 using branch nip91-group-channels.