MongoDB Structure for message app

Question

I am breaking my mind up thinking about a good document structure for handling a message app.

I basically need three (or four) types of objects:

1. The user (

Answer 1

this is my suggestion

{
"_id" : ObjectId("5a9e9581a2147c0c0f00002e"),
"id_members1" : "5a9e9581a2147c0c0f02345t",
"id_members2" : "5a9e9581a2147c0c0f02134g",
"name" : [ 
    "Omar", 
    "Mohamed"
],
"messages" : [ 
    {
        "author" : "Omar",
        "body" : "salam 3likom",
        "create_at" : ISODate("2018-03-07T09:04:04.000Z")
    }, 
    {
        "author" : "Mohamed",
        "body" : "Wa3likom salam",
        "create_at" : ISODate("2018-03-07T09:04:04.000Z")
    }, 
    {
        "author" : "Mohamed",
        "body" : "wach teshak",
        "create_at" : ISODate("2018-03-07T09:04:04.000Z")
    }, 
    {
        "author" : [ 
            "Omar", 
            "Mohamed"
        ],
        "body" : "test msg",
        "create_at" : ISODate("2018-03-25T15:30:05.000Z")
    }
],
"comments" : [ 
    null, 
    {
        "author" : [ 
            "Omar", 
            "Mohamed"
        ],
        "body" : "test msg",
        "create_at" : ISODate("2018-03-25T15:28:11.000Z")
    }, 
    {
        "author" : [ 
            "Omar", 
            "Mohamed"
        ],
        "body" : "test msg",
        "create_at" : ISODate("2018-03-25T15:28:31.000Z")
    }
]

}