I am beginner Node.JS and Mongoose programmer. So far I have created a very simple blog with 3 Models - Article, User, Categories and everything is working fine. Now I want to create comments. So I want every user to be able to have manny comments and every articles also to be able to have manny comments. How can I do that and how can I represent logic in the controller to interact with each other:

let articleSchema = mongoose.Schema (
{
    author: {type: ObjectId, ref: 'User'},
    title: {type: String, required: true },
    content: {type: String, required: true },
    category: {type: ObjectId, ref: 'Category', required: true},
    date: {type: Date, default: Date.now() },
}
);

let userSchema = mongoose.Schema(
{
    email: {type: String, required: true, unique: true},
    passwordHash: {type: String, required: true},
    fullName: {type: String, required: true},
    salt: {type: String, required: true},
    articles: [{type: ObjectId, ref: 'Article'}],
    roles: [{type: ObjectId, ref: 'Role'}]
}
);

let categorySchema = mongoose.Schema (
{
    name: {type: String, required:true},
    articles: [{type: ObjectId, ref: 'Article'}]
}
);