New step: parse_url

[wojtekmach]

In curl, these three invocations are equivalent:

$ curl http://localhost:4000/api
$ curl localhost:4000/api
$ curl :4000/api

let's add a parse_url step that will fill in the missing scheme and host.

[wojtekmach]

This step could make working with UNIX sockets more convenient too:

Instead of:

Req.get!("http:///v1.41/images/json", unix_socket: "/var/run/docker.sock")

do:

Req.get!("http+unix:///var/run/docker.sock/v1.41/images/json")

(or: "http+unix://%2Fvar%2Frun%2Fdocker.sock/v1.41/images/json", see: whatwg/url#577)

[wojtekmach]

This step should perhaps automatically set request.path to "/" if it was empty.

Nevermind, that would seem to be against https://datatracker.ietf.org/doc/html/rfc3986#section-3.3.

[wojtekmach]

Let's hold off on this for now>