Provide OCC command for deleting calendars

[Dieter15]

According to NC documentation https://docs.nextcloud.com/server/20/admin_manual/configuration_server/occ_command.html there is no OCC command for deleting / removing a calendar.

Is your feature request related to a problem? Please describe.
Feature request not related to a problem, at least not to a known problem.

Describe the solution you'd like

1. Provide an OCC command for deleting / removing a calendar for a given NC user
2. Provide an OCC command for deleting / removing the birthday calendar of a given NC user
3. Extend NC documentation to cover the two newly requested commands.

Describe alternatives you've considered
I don't know of any alternatives (except the GUI).
Note: I know that one can delete a calendar and also the birthday calendar. However, sometimes there is a need to flush duplicates in the birthday calendar. I'd appreciate if I could do all the necessary steps in a script.

Additional context
No additional context.