How to make a custom marshaller for JSON API

akka-http-jsonapi.scala

case class MyData(id: String, d: Int)

object MyData {
  implicit def dataMarshaller: ToEntityMarshaller[MyData] = {
    Marshaller.StringMarshaller.wrap(MediaTypes.`application/vnd.api+json`)(data => {
      val jo = JsObject("data" ->
        JsObject("type" -> JsString("dashboard"), "id" -> JsString(data.id),
          "attributes" -> JsObject("exposure" -> JsNumber(data.d)))
      )
      jo.compactPrint
    })
  }
}

object Server extends App with SprayJsonSupport {
  implicit val system = ActorSystem()
  implicit val materializer = ActorMaterializer()
  implicit val ec = system.dispatcher
  import MyData._

  val route =
    path("api" / "dashboards" / Segment) { date =>
      get {
        complete {
          MyData("1", 10000)
        }
      }
    }

  val bindingFuture = Http().bindAndHandle(route, "0.0.0.0", 4100)
}