fix(core-flows, dashboard): adjust stock levels when doing partial fulfilments (#9736)

* fix: correctly update stock location when partial fulfillemnt is created

* fix: update test

* fix: count reserved quantity of the item as available quantity for fulfillment

* fix: refresh reservations when order fulfillment is created

* feat: add check for reservation quantity

* feat: add a test case

packages/core/core-flows/src/order/workflows/create-fulfillment.ts

@@ -202,20 +202,27 @@ function prepareInventoryUpdate({
 
     const inputQuantity = inputItemsMap[item.id]?.quantity ?? item.quantity
 
-    const quantity = reservation.quantity - inputQuantity
+    if (MathBN.gt(inputQuantity, reservation.quantity)) {
+      throw new MedusaError(
+        MedusaError.Types.INVALID_DATA,
+        `Quantity to fulfill exceeds the reserved quantity for the item: ${item.id}`
+      )
+    }
+
+    const remainingReservationQuantity = reservation.quantity - inputQuantity
 
     inventoryAdjustment.push({
       inventory_item_id: reservation.inventory_item_id,
       location_id: input.location_id ?? reservation.location_id,
-      adjustment: MathBN.mult(item.quantity, -1),
+      adjustment: MathBN.mult(inputQuantity, -1),
     })
 
-    if (quantity === 0) {
+    if (remainingReservationQuantity === 0) {
       toDelete.push(reservation.id)
     } else {
       toUpdate.push({
         id: reservation.id,
-        quantity: quantity,
+        quantity: remainingReservationQuantity,
         location_id: input.location_id ?? reservation.location_id,
       })
     }