Standardised format and API for import/export of all non-repo user data

[DavidBuchanan314]

Is your feature request related to a problem? Please describe.

If you wanted to migrate to a new instance, you'd lose things like your mutes and content visibility settings unless you manually copy them over. As time goes on and more features are added, there will be more things stored outside of the repo (e.g. bookmarks?).

This feature might even be required by the GDPR (article 20, Right to data portability), although I can't speak with authority on such things.

Describe the solution you'd like

An API analogous to com.atproto.sync.getRepo, but for all bsky-specific things that aren't stored in the repo, which returns data in some standardised format (also wrapped in a CAR archive I suppose?). Something like app.bsky.???.getUserData. This would require authentication, of course.

Describe alternatives you've considered

Right now you could write a script to call app.bsky.actor.getPreferences and app.bsky.graph.getMutes (and anything else I forgot!) to back up your settings, but that will only get more cumbersome as the list of things you might want to export gets longer.

[DavidBuchanan314]

Here #1672 an interesting idea is mentioned - a "private repo" alongside the public one. This would make it much easier to gather up all the "extra" data in one place, for account migrations