Updates a variant. Send only the fields you want to change. Requires a producer access token for the application.

The product must be unpublished or in draft, because a published product can't have its variants edited. The type-specific fields follow the same rules as Create Variants, so a field that doesn't match the product's product_type is rejected. provider_product_id can't be changed after the variant is created.

images and attributes are full replacements. Send the complete list, and send an empty list to clear them. On a unique-code product, coupon_codes replaces the pool of available codes, and redeemed codes are never touched. Omit it to leave the pool alone, or send an empty list to clear the available codes.