fix(scheduler): set getFirstDayOfWeek instead of option('firstDayOfWeek')

Author: Maksim Zakharov

packages/devextreme/js/__internal/scheduler/m_scheduler.ts

@@ -37,6 +37,7 @@ import { dateUtilsTs } from '@ts/core/utils/date';
 
 import { createA11yStatusContainer } from './a11y_status/a11y_status_render';
 import { getA11yStatusText } from './a11y_status/a11y_status_text';
+import type { AppointmentFormScheduler } from './appointment_popup/form';
 import { AppointmentForm } from './appointment_popup/form';
 import { AppointmentPopup } from './appointment_popup/popup';
 import AppointmentCollection from './appointments/m_appointment_collection';
@@ -1132,7 +1133,7 @@ class Scheduler extends SchedulerOptionsBaseWidget {
   }
 
   createAppointmentForm() {
-    const scheduler = {
+    const scheduler: AppointmentFormScheduler = {
       getResourceById: () => this.resourceManager.resourceById,
       getDataAccessors: () => this._dataAccessors,
       // @ts-expect-error
@@ -1141,7 +1142,7 @@ class Scheduler extends SchedulerOptionsBaseWidget {
       getEditingConfig: () => this.editing,
       getResourceManager: () => this.resourceManager,
 
-      getFirstDayOfWeek: () => this.option('firstDayOfWeek'),
+      getFirstDayOfWeek: () => this.getFirstDayOfWeek(),
       getStartDayHour: () => this.option('startDayHour'),
       getCalculatedEndDate: (startDateWithStartHour) => this._workSpace.calculateEndDate(startDateWithStartHour),
       getTimeZoneCalculator: () => this.timeZoneCalculator,