Create a customer discount link [write]

Pass exactly one of customer_multiplier (one share of public price for every model, 0.01 to 100) or sku_prices (a multiplier, or for SECOND-only SKUs an exact second_usd_per_unit, per SKU). No price may be below your own (400 below_floor) or leave less than 15% over supplier cost on your route (400 below_margin, which names the lowest passing price); a SKU you leave at its default price is raised to that minimum. With audience_email the link is emailed to that customer and redeems once; email_status says whether the email was sent. max_redemptions defaults to 100 and expires_in_days to 30. 403 not_eligible without an eligible discount plan, 429 rate_limited after 20 emailed links in an hour, 503 unavailable while referral pricing is paused. A workspace key or a restricted credential cannot create links.