Set a crontab schedule for Background Tasks

[skttl]

I just remembered, I have an old WIP PR brewing that adds the ability to set background tasks using a crontab schedule instead of the period and delay TimeSpans we have today.

This is especially useful for things like, importing content, doing regular cleanups etc, but with the added security that it only runs when expected.

The current way of having a period and a delay can make the task run in all kinds of times, depending on when your app starts. With a crontab based schedule, you can enforce things like content import to only happen at 3AM eg.

You can see the changes here: v9/contrib...skttl:cronbased-recurring-services

Could something like this be useful?