chore(order): preview order change (#8025)

What:
 - new method `previewOrderChange`
   - Calculate all the actions related to an order change.
   - Return the preview of the final Order, with all the calculated values.
   - Associate actions with items and shipping_methods they modified.

FIXES: CORE-2509

packages/modules/order/src/services/actions/create-claim.ts

@@ -174,6 +174,7 @@ async function processAdditionalItems(
         reference_id: item.id,
         claim_id: claimReference.id,
         quantity: addedItem.quantity,
+        unit_price: item.unit_price,
         metadata: addedItem.metadata,
       },
     })

packages/modules/order/src/services/actions/create-exchange.ts

@@ -129,7 +129,9 @@ async function processAdditionalItems(
 
   createItems.forEach((item, index) => {
     const addedItem = itemsToAdd[index]
+
     additionalNewItems[index].item_id = item.id
+
     actions.push({
       action: ChangeActionType.ITEM_ADD,
       exchange_id: exchangeReference.id,
@@ -140,6 +142,7 @@ async function processAdditionalItems(
         reference_id: item.id,
         exchange_id: exchangeReference.id,
         quantity: addedItem.quantity,
+        unit_price: item.unit_price,
         metadata: addedItem.metadata,
       },
     })