Stalwart 1.0 fails every CalendarEvent get and query whose `timeZone`
argument names a zone missing from its time zone database, with
invalidArguments "Invalid timeZone". 0.16 reads such a zone as UTC, so
the calendar kept working there; on 1.0 it would stay empty.
- check the user's zone with a get of no events that rides along with
the session's first calendar list
- once the server refuses the zone, ask in UTC, move the grid's
wall-clock range bounds to UTC as well, and log one console warning
- repeat a read that was refused before the check answered, once, in
UTC
Stalwart lazily creates an account's default calendar on the first request
that touches it. Bulwark's login fires Calendar/get and CalendarEvent/query
concurrently, and on multi-node servers each node can create its own default,
leaving users with two identical "Personal" calendars. Hold later calendar and
address-book requests per account until the first one settles.
Linus Rath