Timezone should be reported in calendar and events
Problem
When a user creates an event, there is no timezone indication which can be confusing since it could be different from local system depending on browser configuration.
Proposal
- display the timezone retrieved from
Intl.DateTimeFormat().resolvedOptions().timeZone
:- in the event form
- globally on the calendar
- make the timezone editable
Contrary to nextcloud, we should only display the timezone in a single point, nextcloud permit to set a different timezone for start time and end time which may be confusing for users.