Extensions had no supported way to call the Engine API. The configured hosts may be socket-activated or TLS-only TCP. Add the org.mobyproject.extension.daemon.api.v0 point. It returns the address of a private unix socket where the daemon serves its regular API handler. daemonapiv0.NewClient helper resolves the point and returns a *client.Client. Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>