fix(pleno-vue): sort OpenCustomerInvoiceTable flattened orders by id ASC

OpenCustomerInvoiceTable.getOrders concatenates orders across the customer's
open_invoices entries without sorting. The downstream InvoiceOrderTable renders
the resulting array in whatever order the parent arrived in, so the rendered
transaction table is non-deterministic across page loads.

Add a defensive ascending sort by id before returning the list.

src/components/displays/superuser/tables/OpenCustomerInvoiceTable.vue

@@ -50,7 +50,16 @@ const getOrders = (object) => {
     let invoice_orders = invoice.objects;
     orders = orders.concat(invoice_orders);
   }
-  return orders;
+  return orders
+    .slice()
+    .sort((left, right) => {
+      const leftId = Number.parseInt(String(left?.id ?? ""), 10);
+      const rightId = Number.parseInt(String(right?.id ?? ""), 10);
+      if (Number.isInteger(leftId) && Number.isInteger(rightId)) {
+        return leftId - rightId;
+      }
+      return String(left?.id ?? "").localeCompare(String(right?.id ?? ""));
+    });
 }
 
 getDepartments();