Allow to define when a task should start in scheduler.yml

[CyberSinh]

According to the documentation, it is possible to define the recurrence of a task with the interval parameter. However, it does not seem possible to specify when (e.g., at what time) the task should be started.

For example, it would be very useful to be able to schedule a backup at 4 a.m. when the load is low, and to repeat this every day.

Spacing out the various backups over time to avoid overloads would be another very useful use case.