Custom Back In Stock implementation

I am working on a custom integration for our custom e-commerce platform and we would like to implement the Back In Stock flow functionality.

I have gone over the docs, including how to Enable Back In Stock For Custom Catalog Feeds and Set Up Back In Stock Via API. All documentation I have found is for the V1 API using the server side endpoint https://a.klaviyo.com/api/v1/catalog/subscribe or the client side endpoint https://a.klaviyo.com/onsite/components/back-in-stock/subscribe.

There is no mention of these endpoints in the API conversion chart. Is there a way to send back in stock subscriptions using the new date-versioned API? If not, what will happen to the legacy endpoints when they reach end of life?