Update a delegation group with bulk users

curl -u admin:admin -X POST -d '{"group": "Administrators","user":"user1,user2,user3"}' -H "Content-Type: application/json" -v http://your.server.url/rest/wittified/delegated-groups/1.0/delegation/my-group/bulk

Adding a group of users to the group

{
   "status": "success",
    "usersAdded": 4
}

Whitelist group check/Invalid User response

{
      "status": "success",
      "usersAdded": 3,
      "unknownUsers/usersNotInWhitelistedGroups": ["user500"]
}