Updates an event. Send only the fields you want to change inside a calendar_event object:
title, description, start_time, end_time, location, appointment_type, eventable_type
and eventable_id (send both blank to unlink it), user_id to reassign it, and adjuster (as
when creating one). The double-booking check applies when the time or user changes.

If the homeowner was already sent an invite, changing the time or the assigned user sends them an
updated one. Changes are copied to the user's connected Google Calendar or Outlook.

You can update your own events; updating someone else's requires a role that can act on every
record. A validation failure returns 422 with an errors list.