login_admin($self, $email, $password)

Logs you in to the shop as an admin, allowing you to create and manipulate discount codes, as well as upload files into user-space (not theme space).

Doens't get around the API call limit, unfortunately.

logged_in_admin($self)

Determines whether or not you're logged in to the Shopify store as an admin.

As of 2017-08-29, some stores will go for Menus, some for LinkList. This figures out which.