feat(core-flows,types): Refunds can only be performed when order is imbalanced (#8944)

* feat(core-flows,types): Refunds can only be performed when order is imbalanced

* Apply suggestions from code review

Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

* chore: fix tests

---------

Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

integration-tests/http/__tests__/fixtures/order.ts

@@ -149,6 +149,7 @@ export async function createOrderSeeder({ api }) {
     await api.post(`/store/carts`, {
       currency_code: "usd",
       email: "tony@stark-industries.com",
+      region_id: region.id,
       shipping_address: {
         address_1: "test address 1",
         address_2: "test address 2",