version being used (HTTP/1.1, HTTP/2). The old name of this method was
    misleading; it was always used to configure redirects between `https://` and
    `http://` schemes.

 *  **RouteDatabase is no longer public API.** OkHttp continues to track which
    routes have failed but this is no exposed in the API.

 *  **ResponseSource is gone.** This enum exposed whether a response came from