Marks a paid order item as delivered, moving it from redeemed to fulfilled. It takes no request body. Requires a producer access token for the application.

Only an item in redeemed can be fulfilled. Any other state fails with 422 and an error_code. Built-in products (badge, multiplier, flair and coupon-code lines) settle at order time and have no manual steps, so they fail with 400 PRODUCT_NOT_ACTIONABLE. The response is the updated order item, in the same shape as Retrieve Order Item.