CronSchedule.monthlyAt constructor
Builder: Monthly at specific date and time
Example: CronSchedule.monthlyAt(day: 1, hour: 9) → 1st of month at 9 AM
Implementation
factory CronSchedule.monthlyAt({required int day, required int hour, int minute = 0}) {
if (day < 1 || day > 31) throw ArgumentError('Day must be 1-31');
if (hour < 0 || hour > 23) throw ArgumentError('Hour must be 0-23');
if (minute < 0 || minute > 59) throw ArgumentError('Minute must be 0-59');
return CronSchedule('$minute $hour $day * *');
}