[FIX] web: calendar: first day of the week

Before this commit, the calendar view showed Sunday as the
first day of the week.
Now it depends on the user lang.
This is the same behavior that we had before the refactoring
of views.

addons/web/static/src/js/views/calendar/calendar_model.js

@@ -373,6 +373,7 @@ return AbstractModel.extend({
             monthNamesShort: moment.monthsShort(),
             dayNames: moment.weekdays(),
             dayNamesShort: moment.weekdaysShort(),
+            firstDay: moment().startOf('week').isoWeekday(),
         };
     },
     _getRangeDomain: function () {