Mongose array inside of array - arrays

Question

I want to achieve like this:
On every user there's subject, and on every subject there's students.
user: [{ subjects: {subjectCode, description},[{students: {name, year, phone}}]}]
I already got the users -> subject side.
my problem now is how can i achieve to create students inside of subjects?
This is for my authentication.
User.js
const mongoose = require('mongoose');
const UserSchema = mongoose.Schema({
name: {
type: String,
required: true,
},
email: {
type: String,
required: true,
unique: true,
},
password: {
type: String,
required: true,
},
date: {
type: Date,
default: Date.now,
},
});
module.exports = mongoose.model('user', UserSchema);
Every user can create subjects.
Subject.js
const mongoose = require('mongoose');
const SubjectSchema = mongoose.Schema({
user: {
type: mongoose.Schema.Types.ObjectId,
ref: 'users',
},
student: [
{
type: mongoose.Schema.Types.ObjectId,
ref: 'student',
},
],
title: {
type: String,
required: true,
},
description: {
type: String,
},
date: {
type: Date,
default: Date.now,
},
});
module.exports = mongoose.model('subject', SubjectSchema);
In every subjects, there's should array of students.
Student.js
const mongoose = require('mongoose');
const StudentSchema = mongoose.Schema({
user: {
type: mongoose.Schema.Types.ObjectId,
ref: 'users',
},
name: {
type: String,
required: true,
},
year: {
type: String,
},
phone: {
type: String,
},
email: {
type: String,
required: true,
},
date: {
type: Date,
default: Date.now,
},
});
module.exports = mongoose.model('student', StudentSchema);