Turns a design token from create_business_card_design plus the buyer's chosen pack options and email into a Shopify checkout URL, with the print-ready artwork attached to the line item. Call this only after the buyer has approved both design previews and chosen a value for every customer-facing option get_product lists for the business card product (for example Corners and Quantity). selectedOptions must include every option get_product lists, keyed by option name with the buyer's chosen value exactly as listed there. Requires approvalId from approve_design_proof for the same artwork and configuration, plus a quoteToken from get_quote confirmed by the buyer. One approval creates one purchase attempt; retries must keep the same approval, buyer and purchase terms. Uncertain outcomes require recovery, never a replacement purchase. Expired, altered or changed quote terms stop checkout; request a fresh quote and renewed confirmation. For a changed price on an existing purchase, keep the same buyer/artwork/options and set confirmUpdatedQuote:true only after explicit customer confirmation of the fresh quote. This reuses the original purchase/cart; unknown cart outcomes stay on hold. Shopify verifies the resulting cart subtotal before any payment link is returned, then confirms final shipping, tax, discounts and payable total in checkout. Returns quoteId, quotedSubtotal, checkoutUrl, cartId, designAssetId, and lineItem { productTitle, variantTitle, packPrice, currency, selectedOptions }. Fails with quote_required, quote_invalid, quote_expired, quote_changed, quote_unavailable, access_denied, design_token_invalid, design_token_expired, design_not_found, unknown_template, product_unavailable, variant_unavailable {selectedOptions, availableOptions}, rate_limited {retryAfterSeconds}, storage_failed, cart_create_failed, or connector_unavailable.