[#337] added timezone loading from backend (#386)

* [#337] added timezone loading from backend

* [#337] changed data structure to allow patching timezone while keeping other datetime params value

* [#337] fixed gap, event create modale sync with settings and added checkbox

* [#337] isBrowserDefaultTimezone is set to true when API return null timezone

Co-authored-by: Camille Moussu <cmoussu@linagora.com>

src/utils/timezone.ts

@@ -6,6 +6,9 @@ import ICAL from "ical.js";
 // TIMEZONES data must be imported or defined separately.
 import { TIMEZONES } from "./timezone-data";
 
+export const browserDefaultTimeZone =
+  Intl.DateTimeFormat().resolvedOptions().timeZone;
+
 // Core timezone registration functionality
 export function registerTimezones() {
   for (const [key, data] of Object.entries(TIMEZONES.zones)) {