We have a recently created a store that was set up to use Checkout Extensibility and we want to validate that any fields only contain latin characters.
Our older stores had this capability because we use Shopify Plus and were able to use the javascript in our theme liquid code to only allow certain characters in any field on the checkout form.
However, when contacting Support to activate our liquid code on the new store, we were informed that we can no longer use the liquid code on the new store and only Checkout Extensibility is available for that new store to customize the checkout experience.
How would one use Checkout Extensibility to validate existing fields on the checkout form? Looking through the Checkout Extensibility tutorials, I have only been able to find examples of adding new fields and validating them, but unable to find any resources on how validation against existing fields would be done. Please advise.