configuring only OkHttp's TLS sockets.
 *  Fix: Prefer TLSv1.2 where it is available. On certain older platforms it is necessary to opt-in
    to TLSv1.2.
 *  New: `Request.tag()` permits multiple tags. Use a `Class<?>` as a key to identify tags. Note
    that `tag()` now returns null if the request has no tag. Previously this would return the
    request itself.
 *  New: `Headers.Builder.addAll(Headers)`.