I can create a group fine using this Jquery POST;
livelinkURL/otcs/cs.exe/api/v1/members/
var form = new FormData();
form.append("type", "1");
form.append("name", "TestGroup2");
form.append("group_id", "31924");
When i change the Type to "0" to denote a user i get "Bad Request" for the response.