I posted a suggestion for this solution a while back: https://lists.kolab.org/pipermail/users/2015-September/019990.html
Now I needed to do it myself, in a multi-domain scenario: creating many user accounts from a list of names.
I used https://cgit.kolab.org/pykolab/tree/pykolab/cli/cmd_add_user.py for inspiration…
This is the code I came up with:
A sample call looks like this:
python createusers.py example.org de_DE "von und zu Berlin" "Heinrich" topsecreat