Create a new product swap automation

Creates a new product swap automation rule for the authenticated shop. Product swaps automatically replace products in subscription orders based on billing cycles or recurring schedules. <details> <summary>**Full behavior, validation rules, and side effects**</summary> **Required Fields:** - **shop**: Your Shopify shop domain - **sourceVariants**: JSON string of variants to swap FROM (format: [{"id":12345,"quantity":2}]) - **destinationVariants**: JSON string of variants to swap TO (format: [{"id":67890,"quantity":2}]) - **name**: Descriptive name for this swap rule **Optional Fields:** - **forBillingCycle**: Specific cycle number when swap occurs (e.g., 4 = swap at 4th order). Leave null for recurring swaps. - **checkForEveryRecurringOrder**: If true, applies swap to every order (overrides forBillingCycle) - **updatedFirstOrder**: If true, can affect the first subscription order - **changeNextOrderDateBy**: Days to adjust next order date after swap (positive or negative integer) - **discountCarryForward**: How to handle discounts - NONE, PERCENTAGE, FIXED_AMOUNT, or PRICE - **carryDiscountForward**: Legacy boolean field (deprecated, use discountCarryForward instead) - **stopSwapEmails**: If true, suppresses customer notification emails about the swap - **ruleSequence**: Priority order when multiple swaps apply (lower number = higher priority) **Variant JSON Format:** The API enriches your variant data with product details from Shopify. You only need to provide: ```json [{"id": 12345, "quantity": 2}] ``` The response will include enriched data: displayName, imageSrc, productTitle, etc. **Authentication:** Requires valid X-API-Key header </details>