如何在play框架中编写填充了异步mongodb查询的嵌套case类

case class User(name: String, age: Int)
case class Comment(content: String, user: User)
case class Post(title: String, comments: List[Comment])

import javax.inject.Inject
import play.api.libs.concurrent.Execution.Implicits.defaultContext
import play.api.libs.json.Json
import play.modules.reactivemongo.ReactiveMongoApi
import reactivemongo.play.json.collection.JSONCollection

class MyController @Inject()(val reactiveMongoApi: ReactiveMongoApi) extends Controller {
  def getPosts = Action.async {
    val collection: JSONCollection = reactiveMongoApi.db.collection[JSONCollection]("posts")

    val query = Json.obj("title" -> "Play Framework")
    val projection = Json.obj("_id" -> 0, "title" -> 1, "comments" -> 1)
    
    collection.find(query, projection)
      .cursor[JsObject]()
      .collect[List]()
      .map { posts =>
        val result = posts.map { post =>
          val title = (post \ "title").as[String]
          val comments = (post \ "comments").as[List[JsObject]].map { comment =>
            val content = (comment \ "content").as[String]
            val user = (comment \ "user").as[JsObject]
            val name = (user \ "name").as[String]
            val age = (user \ "age").as[Int]
            Comment(content, User(name, age))
          }
          Post(title, comments)
        }
        Ok(Json.toJson(result))
      }
  }
}

GET /posts    controllers.MyController.getPosts