Update an existing booking. Supports updating the title, time, duration,
description, location, and attendees of the meeting. The underlying calendar
event is updated and participants are notified by default.

Cannot be used on cancelled bookings or to set a start time in the past.

When you change the time, the new slot is validated against the meeting
template it was booked from. The request returns 400, with the reason in the
response message, if the new slot:

• falls outside the template's open hours
• falls inside the template's minimum notice period
• falls beyond the template's booking window
• overlaps another meeting on the assigned interviewer's calendar,
  including the template's buffer either side

Moving a booking within its own existing slot is always allowed. Changes
that do not alter the time are not validated against the template.

The request also returns 400 if the template's rules cannot be read at all —
for example if its scheduler configuration is missing open hours, a notice
period or a booking window, or if the booking's organizer calendar cannot be
resolved. These are reported separately from a rule that was evaluated and
failed, so you can tell "your time is outside the open hours" from "we could
not read this template".

Returns 404 if the booking does not exist, or if it belongs to a different
organisation than the one tied to the API key.