CompostionalHttpApp.scala

def translate(app: HttpApp): HttpApp = {
  app.andThen(future => for {
    resp <- future
    tx <- Translator.future(resp.body)
  } yield resp.copy(body = tx))}

def hello(theUri: Uri): HttpRoutes = HttpRoutes.of {
  case Request(POST, uri, name) if uri == theUri =>
    Future.successful(Response(OK, s"Hello, $name!"))
}
val app: HttpApp = translate(seal(hello(Uri("/hola"))))

// Unit test
val req = Request(POST, Uri("/hola"), "Boston")
// req: Request = Request(POST,Uri(/hola),Boston)
asyncAssert("¡Hola, Boston!", app(req).map(_.body))
// ✔ ¡Hola, Boston!