post https://api.northpass.com/v2/people//relationships/groups
Add existing groups to an existing person.
Depending on the type it will either add a person as a member (membership-groups) or add the groups to the list of managed groups (managed-groups).
This will associate the person with any groups they are not currently associated with and ignore any groups that the person is already associated with. You do not have to include any groups that the person is already associated with, as this will not remove any current associations.