Implement a Loop Returns branded return portal using the Loop API to support variant exchanges and gift card resolutions

Verified steps

1. Authenticate against the Loop Returns API using the merchant API key and retrieve the return window and policy settings to validate whether an order is eligible for return before displaying the portal
2. Create a return via the Loop returns creation endpoint, passing the Shopify order ID, line item IDs, and return reason codes selected by the customer
3. Present the available resolution options returned by the Loop API for each eligible line item: refund to original payment, store credit, or exchange for another variant
4. For exchange resolutions, call the Loop variant availability endpoint to surface in-stock exchange options filtered to the same product or related products based on Loop's configured exchange rules
5. Submit the selected resolution via the Loop returns update endpoint and retrieve the generated return shipping label URL or QR code for display to the customer
6. Subscribe to Loop webhook events for return_received and return_completed to trigger downstream actions such as restocking the returned item in Shopify and issuing the store credit or refund