restAPI add/update isnt working for the user's groups

Ive used the PHP API and even the advanced rest client and in both scenarios, i can add and update everything on the user except their groups.

Not sure if im calling it right or if something is mis-configured. Nothing showed up in the logs as well regarding the calls.

URL:
http://localhost:9090/plugins/restapi/v1/users

HEADERS:

Authorization: 634h27z0Pwf6iMKo

Content-Type:  application/json

Accept: application/json

PAYLOAD:

{   "username": "testuser22",   "password": "p4ssword",   "name": "Administrator",   "email": "admin@example.com","groups":["member"] }