docs: update order module's conceptual guides (#7893)

* fixes + add return document

* update order conceptual guides

* resolve todo

* re-generate files map

www/apps/resources/app/commerce-modules/order/concepts/page.mdx

@@ -20,7 +20,11 @@ The details of the purchased products are represented by the [LineItem data mode
 
 ## Order’s Shipping Method
 
-An order has one or more shipping methods used to handle item shipment. Each shipping method is represented by the [ShippingMethod data model](/references/order/models/ShippingMethod) that holds its details.
+An order has one or more shipping methods used to handle item shipment.
+
+Each shipping method is represented by the [ShippingMethod data model](/references/order/models/ShippingMethod) that holds its details. The shipping method is linked to the order through the [OrderShippingMethod data model](/references/order/models/OrderShippingMethod).
+
+![A diagram showcasing the relation between an order and its items.](https://res.cloudinary.com/dza7lstvk/image/upload/v1719570409/Medusa%20Resources/order-shipping-method_tkggvd.jpg)
 
 ### data Property