Returns one person of the organization users list, with the same fields as a row of organization-users-list. id_or_email is the id of the person's backend user, or their email. Many rows have no backend user: an invitation, a pushed person before the first login, and most people of the tail. The email finds every row. A UUID is read as an id, and any other value as an email, which is compared after trimming and lower-casing. A person that the list does not show answers 404. Requires organization administration permission.