Instead, the user generates the api_endpoint url to set on their device
by visiting http://.../kobo_auth/generate_auth_token.
The generated url will contain a RemoteAuthorizationToken that will be
included on all subsequent requests from the device to the kobo/
endpoints. (In contrast, the device is authenticated using a session cookie on
requests to the download endpoint).
Also use Flask.url_for to generate download urls.