Simple Auth with Finch

auth.scala

scala> case class Auth(u: String)
defined class Auth

scala> val auth = headerOption("Auth").withDefault("anon").as[Auth].mapOutput { a =>
     | if (a.u == "foo") Ok(a) else Unauthorized(new Exception("wrong credentials"))
     | }

scala> val e = get("foo" :: auth).map(_.u)
e: io.finch.Endpoint[String] = GET /foo/header(Auth)

scala> val s = e.toService
s: com.twitter.finagle.Service[com.twitter.finagle.http.Request,com.twitter.finagle.http.Response] = <function1>

scala> s(Request("/foo")).get
res1: com.twitter.finagle.http.Response = Response("HTTP/1.1 Status(401)")

scala> val req = Request("/foo")
req: com.twitter.finagle.http.Request = Request("GET /foo", from 0.0.0.0/0.0.0.0:0)

scala> req.headerMap.set("Auth", "foo")
res2: com.twitter.finagle.http.HeaderMap = Map(Auth -> foo)

scala> s(req).get
res3: com.twitter.finagle.http.Response = Response("HTTP/1.1 Status(200)")

scala> s(req).get.contentString
res4: String = "foo"