Where can I find an OpenAPI schema for Zendesk's Support API?

There's currently no actively-supported strongly-typed Node/JS SDK for the Support API, which I strongly suspect is because there is no known publicly-available OpenAPI schema published for this API. If one were to be published, I could code-gen types, helpers and SDKs for this API. An admin in the support community indicated a couple of years that Zendesk engineers were working on this, and that he would have news for us "shortly" (2 years ago) and now does not respond to further messages in the thread.