MongoDB聚合：如何将查找结果放入嵌套数组中

我正在try 聚合以下文档，以将参与者作为嵌套数组中的对象.

{
  "name": "EXAMPLE",
  "schedules": [
    {
      "schedule_id":  "id1",
      "participants": [
      "participant_id1",
      "participant_id2"
      ],
    },
    {
      "schedule_id": "id2",
      "participants": [
        "participant_id1",
        "participant_id2"
      ],
    },
    {
      "schedule_id": "id3",
      "participants": [
        "participant_id1"
      ],
    },
  ],
}

因此，我写了以下管道:

[
  {
    $unwind: {
      path: "$schedules",
      includeArrayIndex: "index",
      preserveNullAndEmptyArrays: true,
      
    }
  },
  {
    $unwind: {
      path: "$schedules.participants",
      includeArrayIndex: "index",
      preserveNullAndEmptyArrays: true,
      
    }
  },
  {
    $lookup: {
      from: "customers",
      localField: "schedules.participants",
      foreignField: "_id",
      as: "participants",
      
    }
  },
  {
    $project: {
      "participants.address": 0,
      "participants.birthday": 0,
      
    }
  },
  {
    $unwind: {
      path: "$participants",
      preserveNullAndEmptyArrays: true,
      
    }
  },
  {
    $group:
    {
      _id: "$_id",
      name: {
        $first: "$name",
        
      },
      schedules: {
        $first: "$schedules",
        
      },
      
    }
  },
  
]

1. 此管道中的第一步是展开时间表数组，以获得文档中的每个单独时间表.
2. 第二步是展开参与者，因为我需要参与者ID来执行第三步中的查找过程.
3. 第三步是在Customers集合中查找参与者，返回的将是一个Customer对象.
4. 在第四步中，我将使用project从给定参与者中删除不必要的字段.
5. 在第五步中，我再次使用展开来获取单个参与者(我知道也可以使用$First运算符)
6. 在第六步，我将对其进行分组

我正在try 将步骤3中的每个参与者添加到参与者数组中的相应日程对象，即document should be like this:

  {
    "name": "EXAMPLE",
    "schedules": [
      {
        "schedule_id": "id1",
        "participants": [
          {
            id: "id1",
            "name": "name1"
          },
          {
            id: "id2",
            "name": "name2"
          },
          
        ],
        
      },
      {
        "schedule_id": "id2",
        "participants": [
          {
            id: "id1",
            "name": "name1"
          },
          {
            id: "id2",
            "name": "name2"
          },
          
        ],
        
      },
      {
        "schedule_id": "id3",
        "participants": [
          {
            id: "id1",
            "name": "name1"
          },
          
        ],
        
      },
      
    ], 
  }