dav5x fetches account emails from fastmail, and uses those for ORGANIZER
in invites.
We should sync this metadata too so that khal
can use it (probably also for accepting invites).
I think it uses this: https://datatracker.ietf.org/doc/html/rfc6638#section-2.4.1
See:
- https://github.com/bitfireAT/davx5-ose/blob/6b980889228a0410d45382d5c2a9e9ef468804aa/app/src/main/java/at/bitfire/davdroid/ui/setup/DavResourceFinder.kt#L152
- https://github.com/bitfireAT/davx5-ose/blob/6b980889228a0410d45382d5c2a9e9ef468804aa/app/src/main/java/at/bitfire/davdroid/ui/setup/DavResourceFinder.kt#L152