order
    user: {type: Schema.Types.ObjectId, ref: 'User'},
    cart: {type: Object, required: true},
    address: {type: String, required: true},
    name: {type: String, required: true},
    paymentId: {type: String, required: true}

user
    email: {type: String, required: true},
    password: {type: String, required: true}

product
   image: {type: String, required: true},
   title: {type: String, required: true},
   description: {type: String, required: true},
   price: {type: Number, required: true}


cart
    orders arr.reduce()