Currently, the Parsoid API is defiend in RESTBase. Equivalent endpoints implemented in PHP exist in the Parsoid extension under /{domain}/v3/page/html/{title}. Alternative endpoints for retrieving page HTML are exposed by MediaWiki core under /v1/page/{title}/html.
Instead of exposing the parsoid endpoints through RESTBase, we want to expose them through Envoy (REST Gateway or API Gateway)