loginProviders.scala

trait LoginProvider {
  val loginPath: Path // listen for POST on this
  val location: String
  def redirect: Response =
    tap(Response(Status.Found))(_.location = location)
}

case class InternalLoginProvider(path: Path, hosts: String, loginPath: Path) extends LoginProvider {
  val location = path.toString
  val server = Http.newClient(hosts)
}

case class ExternalLoginProvider(url: URL, loginPath: Path) extends LoginProvider {
  val location = url.toString
}