MOOver.js/database/birthdaySchema.js

const mongoose = require('mongoose');

const birthdaySchema = new mongoose.Schema({
    id: {
        type: String,
        unique: true,
    },
    day: Number,
    month: Number,
    nickname: {
        type: String,
        default: '',
    },
});

module.exports=mongoose.model('birthdays', birthdaySchema);