Helper struct that will store the CardSets and a couple HashMaps for fast indexing
This is the top level of the response JSON provided by the Valve API
Artifact deck representation, typically derived from Artifact Deck Codes.
This function will search the user's local cache for the card set data, if not found or out of date, will fetch updates from Valve's API and create and update the cached files. Once that process is complete, it will return a Vec of CardSets.
Returns a HashMap mapping cards' card_ids to the respective card
Returns a HashMap mapping cards' English names to the respective card