User Author List
A combination of an Author associated with a particular user.
Writable Fields:
user: The API URL of the User to associate with this UserAuthor
author: The API URL of the Author to associate with this UserAuthor
Read-only Fields:
url: Reference to the instance of the UserAuthor, final integer is the UserAuthor id
last_updated: Datetime that this record was last updated
updated_by: Reference to the user that updated this record
GET /api/user_author/?format=api
{
    "count": 0,
    "next": null,
    "previous": null,
    "results": []
}