How do you add an employee with account using the REST API?

My goal is to find some way of getting employees and their login accounts added to Virto (without manually keying them). Since I don’t see a way to do that with a CSV import, I turned to the REST API.

I see that I can do a POST to the /api/employees endpoint to successfully add an employee to one or more organizations. However, I don’t see how to add the employee login account, with role, at the same time – or after the fact, for that matter.

Does anyone know how I can do that?