If I understand correctly, you want to modify the group membership of the user, correct me if I am wrong
Try following api call:-
curl -ivk -u admin:admin -H "Content-Type: application/json" -d '{"id":13,"createDate":"2020-12-23T07:55:04Z","updateDate":"2020-12-23T07:55:04Z","owner":"rangerusersync","updatedBy":"rangerusersync","name":"atlas","password":"*****","description":"atlas - add from Unix box","groupIdList":[6,59,4,131,133],"groupNameList":["atlas","hadoop","shadow"],"status":0,"isVisible":1,"userSource":1,"userRoleList":["ROLE_USER"],"otherAttributes":"{\"full_name\":\"atlas\",\"original_name\":\"atlas\"}"}' -X PUT https://RANGER_HOST:6182/service/xusers/users
Its little bit big but if user is already added to ranger then run following api to get the id information for users:-
curl -ivk -u admin:admin -H "Accept : application/json" -X GET https://RANGER_HOST:6182/service/xusers/users
Once you have IDS for all users, you can run following crul api to get the json formatted data which you use to modify and then use PUT method in first API I mentioned:-
curl -ivk -u admin:admin -H "Accept: application/json" -X GET https://RANGER_HOST:6182/service/xusers/users/13
Above Curl api should return something like following:-
{"id":13,"createDate":"2020-12-23T07:55:04Z","updateDate":"2020-12-23T16:45:14Z","owner":"rangerusersync","updatedBy":"admin","name":"atlas","password":"*****","description":"atlas - add from Unix box","groupIdList":[133,6],"groupNameList":["apitest","atlas","hadoop","shadow","ssb"],"status":0,"isVisible":1,"userSource":1,"userRoleList":["ROLE_USER"],"otherAttributes":"{\"full_name\":\"atlas\",\"original_name\":\"atlas\"}"}
you have to modify "groupIdList":[133,6] from the above output copy entire output and pass it with PUT method as shown in the first api call mentioned above.