Feat/decline order edit (#2234)

**What**
- Decline an order edit from a store endpoint
- Refactor totals setting to a service method

Fixes CORE-502

packages/medusa-react/mocks/handlers/store.ts

@@ -69,6 +69,15 @@ export const storeHandlers = [
     )
   }),
 
+  rest.post("/store/order-edits/:id/decline", (req, res, ctx) => {
+    return res(
+      ctx.status(200),
+      ctx.json({
+        order_edit: {...fixtures.get("order_edit"), declined_reason: req.body.declined_reason, status: 'declined'},
+      })
+    )
+  }),
+
   rest.get("/store/orders/:id", (req, res, ctx) => {
     return res(
       ctx.status(200),