Issue with OpenAPIHandler doc route for /openapi.json when using root_path prefix

[jlujan-invitae]

When setting a root_path of "/prefix" on the uvicorn app, the /docs route from the example/template app results in a 404 when attempting to load /openapi.json. Explicitly setting OpenAPIHandler(...,json_spec_path="/prefix/openapi.json") or to a full URL also returns 404.