fix(core-flows): item id in reservations (#9097)

**What**
- on cart completion, when creating reservations, use line item id instead of cart item id
- NOTE: inventory reservation is now done after we create the order

---

FIXES CC-448

integration-tests/modules/__tests__/cart/store/carts.spec.ts

@@ -2238,7 +2238,7 @@ medusaIntegrationTestRunner({
               location_id: stockLocation.id,
               inventory_item_id: inventoryItem.id,
               quantity: cart.items[0].quantity,
-              line_item_id: cart.items[0].id,
+              line_item_id: response.data.order.items[0].id,
             })
           )
 

packages/core/core-flows/src/cart/utils/prepare-confirm-inventory-input.ts

@@ -12,7 +12,7 @@ interface ConfirmInventoryPreparationInput {
   }[]
   items: {
     id?: string
-    variant_id?: string
+    variant_id?: string | null
     quantity: BigNumberInput
   }[]
   variants: {

packages/core/core-flows/src/cart/workflows/complete-cart.ts

@@ -84,26 +84,12 @@ export const completeCartWorkflow = createWorkflow(
       }
     )
 
-    const formatedInventoryItems = transform(
-      {
-        input: {
-          sales_channel_id,
-          variants,
-          items,
-        },
-      },
-      prepareConfirmInventoryInput
-    )
-
-    const [, finalCart] = parallelize(
-      reserveInventoryStep(formatedInventoryItems),
-      useRemoteQueryStep({
-        entry_point: "cart",
-        fields: completeCartFields,
-        variables: { id: input.id },
-        list: false,
-      }).config({ name: "final-cart" })
-    )
+    const finalCart = useRemoteQueryStep({
+      entry_point: "cart",
+      fields: completeCartFields,
+      variables: { id: input.id },
+      list: false,
+    }).config({ name: "final-cart" })
 
     const cartToOrder = transform({ cart }, ({ cart }) => {
       const allItems = (cart.items ?? []).map((item) => {
@@ -162,11 +148,31 @@ export const completeCartWorkflow = createWorkflow(
     })
 
     const createdOrders = createOrdersStep([cartToOrder])
+
     const order = transform(
       { createdOrders },
       ({ createdOrders }) => createdOrders[0]
     )
 
+    const reservationItemsData = transform({ order }, ({ order }) =>
+      order.items!.map((i) => ({
+        variant_id: i.variant_id,
+        quantity: i.quantity,
+        id: i.id,
+      }))
+    )
+
+    const formatedInventoryItems = transform(
+      {
+        input: {
+          sales_channel_id,
+          variants,
+          items: reservationItemsData,
+        },
+      },
+      prepareConfirmInventoryInput
+    )
+
     const updateCompletedAt = transform({ cart }, ({ cart }) => {
       return {
         id: cart.id,
@@ -188,6 +194,7 @@ export const completeCartWorkflow = createWorkflow(
         },
       ]),
       updateCartsStep([updateCompletedAt]),
+      reserveInventoryStep(formatedInventoryItems),
       emitEventStep({
         eventName: OrderWorkflowEvents.PLACED,
         data: { id: order.id },

packages/core/types/src/cart/workflows.ts

@@ -143,8 +143,9 @@ export interface ConfirmVariantInventoryWorkflowInputDTO {
     }[]
   }[]
   items: {
-    variant_id?: string
+    variant_id?: string | null
     quantity: BigNumberInput
+    id?: string
   }[]
   itemsToUpdate?: {
     data: {