fix(core-flows, medusa): don't allow negative line item quantity (#13508)

* fix(core-flows,medusa): don't allow negative line item quantity

* fix: greater than 0

* feat: add test

* wip: update update item flow to remove item when qty is 0

* fix: paralelize

* fix: when argument

* fix: emit event

packages/medusa/src/api/store/carts/validators.ts

@@ -7,7 +7,7 @@ export const StoreGetCartsCart = createSelectParams()
 
 const ItemSchema = z.object({
   variant_id: z.string(),
-  quantity: z.number(),
+  quantity: z.number().gt(0),
   metadata: z.record(z.unknown()).nullish(),
 })
 
@@ -65,7 +65,7 @@ export const StoreCalculateCartTaxes = createSelectParams()
 export type StoreAddCartLineItemType = z.infer<typeof StoreAddCartLineItem>
 export const StoreAddCartLineItem = z.object({
   variant_id: z.string(),
-  quantity: z.number(),
+  quantity: z.number().gt(0),
   metadata: z.record(z.unknown()).nullish(),
 })
 
@@ -73,7 +73,7 @@ export type StoreUpdateCartLineItemType = z.infer<
   typeof StoreUpdateCartLineItem
 >
 export const StoreUpdateCartLineItem = z.object({
-  quantity: z.number(),
+  quantity: z.number().gte(0), // can be 0 to remove the item from the cart
   metadata: z.record(z.unknown()).nullish(),
 })