A user's stack of one item. Items are free-form string codes ("health_potion", "sword", "card_374") — the game decides which exist. metadata holds per-stack properties.
"health_potion"
"sword"
"card_374"
metadata
@type t() :: %Gamend.Inventory.Item{ __meta__: term(), id: term(), inserted_at: term(), item: term(), metadata: term(), quantity: term(), updated_at: term(), user: term(), user_id: term() }