Permissioned-data preview

Last month we got a preliminary spec for permissioned data in atproto:
https://dholms.leaflet.pub/3mhj6bcqats2o

The roomy team has been evaluating this proposal in the context of communities:
https://meri.leaflet.pub/3mj4qwvypq22a

We've arrived at a preliminary spec of our own, extending the permissioned data proposal with the notion of an 'arbiter':
https://zicklag.leaflet.pub/3mjrvb5pul224

In discussing this with the tranquil team on chat, we seem to agree it makes sense to follow this up with an implementation in tranquil to lead the way for permissioned data developed by the atproto community:

nelind: pulling the spec in a direction that means it can actually be as useful as possible to the people who are making apps that need permissioned data should be the main goal

tranquil exists in part to be the a place where the community can show PBC what we wish we had so doing something like this in tranquil in some way shape or form makes sense to me

For next steps, zicklag is completing our spec for permissioned data with the arbiter and will work on a sans-io state machine validated against our formal Quint specification.

Also instructive here is contrail by @flo-bit.dev which, while still in the playground stage, has sketched out its own specs for spaces and communities (based on the arbiter).