3815143 - How do I assign a user to an employee group with the User Provisioning API v4?

I need to add an employee group to a spend user with SAP Concur APIs. I see that employee group assignment is driven by a custom field, but I am not sure whether I need to set a specific value or remove the field from the payload. I want to know the correct way to assign a user to a group.

Explains how to assign a user to the employee group through the User API and the spend user extension. The group is generally determined by the value of custom21. , KBA , CON-INT , Integrations , Problem