{

    "ToUserName":"ww725c57b80f143xxx",

    "FromUserName":"sys",

    "CreateTime":"1676357852",

    "MsgType":"event",

    "Event":"change_external_chat",

    "ChatId":"wrkmY4HgAAkcce3VAN12RwXXxxxxxxxx",

    "ChangeType":"update",

    "UpdateDetail":"add_member",

    "JoinScene":"0",

    "MemChangeCnt":"2"

}

怎么才能知道是哪个人加群或者退群了？