Align the test REST API client following NXP-22542

{
  "entity-type":"group",
  "id": "GROUP_NAME",
  "properties": {
    "groupname":"GROUP_NAME",
    "grouplabel":"GROUP_DISPLAY_NAME",
    "description": "GROUP_DESCRIPTION"
  },
  "memberUsers": [ "USERNAME1", "USERNAME2", ... ],
  "memberGroups": [ "GROUPNAME1", "GROUPNAME2", ... ],
  "parentGroups": [ "GROUPNAME1", "GROUPNAME2", ... ]
}