Gets the available item field values (VAT rates, item attributes, payment types, shipping types). The item attributes returned here are the coarse condition flag only (1 = Ny, 2 = Begagnad), set via `ItemRequest.ItemAttributes`. Finer, category-specific condition values such as the "Skick" selector on the sell form (Oanvänt, Mycket gott skick, …) are category attributes, not item field values: fetch them from `GET categories/{categoryId}/attribute-definitions` and submit them via `ItemRequest.AttributeValues.Terms`.