Out of office: jcoffey-dev is traveling from November 1 to November 6. Responses to issues may be slow or delayed during this time, but I will be checking in.
A confidential event (CLASS:CONFIDENTIAL) was treated as secret: for
anyone the calendar was shared with it didn't exist. CalDAV clients
such as Thunderbird use CONFIDENTIAL for "show time and date only", so
their users' events vanished from sharees' calendars instead of showing
as busy time. Events are stored as iCalendar, where a JMAP "secret"
event is also CLASS:CONFIDENTIAL, so the two can't be told apart.
A confidential event, whether set over CalDAV or as JMAP "secret", now
shows sharees what a private event does: its time, recurrence and basic
metadata only. Matching it on title, description, location or
participants finds nothing, copying it out is refused, and its blob is
not downloadable by sharees. The owner still sees all of it.
Test: a sharee got notFound for a confidential event and couldn't list
it; now it is listed and shows its start and duration only, with no
title, description or participants, isn't found by title, and can't be
copied, as for a private event.