[FeatureRequest] ScalingSchedule: add crontab schedule

[jgournet]

The current options "OneTime" and "Repeating" do not allow the same flexibility as using a classic crontab/cronjob style
=> would it be possible to add this ?

Notes:

1. thanks for adding that ScalingSchedule ! really appreciated
2. example use case: "schedule every first day of the Month at 1am" => "0 1 1 * *" : this is something easily done in cronjob, but can't be done with the current ScalingSchedules; and since cron is ubiquitous in modern (linux) world, I hope this feature request is not too far fetched