StandaloneAhcWSRequest.createProxy should setUsePreemptiveAuth(true) for basic auth

[halfhp]

Play WS Version

1.1.10

API (Scala / Java / Neither / Both)

Scala

Expected Behavior

Requests that specify a Proxy with basic auth should setUsePreemptiveAuth(true) for the proxy realm.

Actual Behavior

Requests that specify a Proxy with basic auth never setUsePreemptiveAuth(true) for the proxy realm, causing the connection to fail.

Details / Steps to Reproduce

While unsuccessfully attempting to connect to a commercial proxy using basic auth I noticed that StandaloneAhcWSRequest is inconsistent in it's application of realm configuration; for non-proxy requests usePreemptiveAuth is always set to true for non DIGEST schemes, however, when making a proxy request, this logic is omitted.

Upon duplicating the scheme check logic in StandaloneAhcWSRequest.createProxy() my basic auth proxy requests began working.

This is the code I've been using to test:

  val proxy = DefaultWSProxyServer(
    host = "some.proxy.xx",
    port = 222,
    principal = Some("username"),
    password = Some("password"))

  wsClient
    .url("http://api.ipify.org")
    .withProxyServer(proxy)
    .get().map( _.body[String])

If someone with more knowledge about how this code should be working can validate my findings, I'd be happy to issue a PR with a fix :-)