Returns one variant of a product. Reads are public, so no producer token is needed. A deleted variant returns 404.

has_discount is true when discount_percentage is set, and discounted_cost is the cost after the discount. available_count is the stock left, and for a unique-code variant it is the number of unredeemed codes. display_status is one of available, few_left, sold_out, coming_soon or expired. The last two follow the parent product's start and expiry dates. coupon_code_count, available_coupon_code_count and redeemed_coupon_code_count count the codes of a unique-code variant. The codes themselves are never returned.