copyWith method Null safety
- {ScheduleRequestStatus? status,
 - Schedule? schedule,
 - String? errorMessage,
 - int? selectedDay}
 
Implementation
ScheduleState copyWith({
  ScheduleRequestStatus? status,
  Schedule? schedule,
  String? errorMessage,
  int? selectedDay,
}) {
  return ScheduleState(
    status: status ?? this.status,
    schedule: schedule ?? this.schedule,
    errorMessage: errorMessage ?? this.errorMessage,
  );
}