mongoose聚合查找数组

Question

我的项目集合如下所示：

{
    country: "usa",
    notes: [
        {
            user:ObjectId("..."),
            text:"asdasdasd"
        },
                    {
            user:ObjectId("..."),
            text:"asdasdasd"
        }
    ],
    etc...
}

另外用户收藏：

{
    _id: ObjectId("..."),
    firstname: "simon",
    etc...
}

我想查找用户以获取notes对象的结果：

notes: [
        {
            user:{
                _id: ObjectId("..."),
                firstname: "simon"
            },
            text:"asdasdasd"
        },
        {
            user:{
                _id: ObjectId("..."),
                firstname: "..."
            },
            text:"asdasdasd"
        }
    ],

我该如何查找？