Bonus.scala

@assemble class ByPKAssemble extends Assemble {
  def byPKRequestWithSrcToItemSrcId(
    key: SrcId,
    rq: Each[DepInnerRequest]
  ): Values[(ByPkItemSrcId, InnerByPKRequest)] =
    if(!rq.request.isInstanceOf[ByPKRequest]) Nil else {
      val brq = rq.request.asInstanceOf[ByPKRequest]
      List(brq.itemSrcId → InnerByPKRequest(rq, brq.className))
    }
}

@assemble class ByPKGenericAssemble[A <: Product](handledClass: Class[A], util: DepResponseFactory) extends Assemble {
  def BPKRequestToResponse(
    key: SrcId,
    @by[ByPkItemSrcId] rq: Each[InnerByPKRequest],
    items: Values[A]
  ): Values[(SrcId, DepResponse)] =
    if(rq.className != handledClass.getName) Nil
    else List(WithPK(util.wrap(rq.request, Option(items.toList))))
}