New resource: split_user_group_association

[davidji99]

You remove a user from a group by using the patch and sending an ‘op’ of ‘remove’ like the below: (note that the order of the group you’re removing does matter so removing group /groups/0 is the first group that the user has, /groups/1 is the second and so on)

[{
"op": "remove",
"path": "/groups/1",
}]