APIs for updating the partner login for Partner Organization Users

Summary:

We're looking for APIs REST/SOAP to update the MR Users (Partner Organizations) partner login, we want to update the partner login even in cases when this field is frozen on the UI which happens when the token is generated.
Here is how to reach this field in CPQ: Admin-->Users-->Partner Organizations-->List-->Login

Content (please ensure you mask any confidential information):
We require API to:
1. Update this 'partner login' field for Partner Organizations
2. Unfreeze this field in CPQ (in case token is generated) to revoke the token.
PFA the SS of the Partner Login field in CPQ UI