I'm learning mongo from absolute scratch, and i can't for the hell of it figure out how to create a collection with predefined variables. I need to do that in order to have unique mails on my project. Any help would be very appreciated.

I'm trying to do a basic CRUD, and everything you see in the code is a lot of different tutorials combined into one, so far I'm able to create new users, and obtain a list of all of them, but in order to delete one or edit/update one I really need an unique attribute.

This is my code if it is useful:

    const express= require ('express');
    var mongoose = require('mongoose');
    var Schema = mongoose.Schema;
    const app = express();
    const cors = require('cors');
    const bcrypt = require('bcrypt');
    const MongoClient = require('mongodb').MongoClient;
    const saltRounds=10;

    app.use(cors());
    app.use(express.json());
    app.listen(3001,()=>{
        console.log("Welcome");
    });



    // CONEXION BASE DE DATOS
    MongoClient.connect('mongodb+srv://admin:admin@cluster0.bs9d2.mongodb.net/test?retryWrites=true&w=majority'
    ,{ useUnifiedTopology: true }).then(client=>{

        console.log('Bienvenido a database mongo');
        const db = client.db('ezbuy-database');
        const usersCollection = db.collection('users');

       

       
        /*Añade un usuario nuevo a la BD*/
        /*Falta ver como hacer datos unicos, pero no se como*/
         
        app.post('/newuser', (req, res) => {
            const userObject ={
            
                name: req.body.name,
                identification:req.body.identification,
                email:req.body.email,
                password:req.body.password,
                cellphone:req.body.cellphone,
                addedDate:req.body.addedDate,
                lastLoginDate:req.body.addedDate,
                role:req.body.role,
                speciality:req.body.speciality
               }
             ;
            bcrypt.hash(userObject.password,saltRounds,(err,hash) => {
                if(err){console.log(err)}
               userObject.password=hash;
               
               usersCollection.insertOne(userObject)
              .then(result => {
                console.log(result);
                console.log("Dato Añadido a mongo  ");
                res.send('Usuario Creado');
              })
              .catch(error => console.error(error))
           
            })
            })
            
            /*Devuelve todos los usuarios creados*/
            app.get('/allusers', (req, res) => {
              db.collection("users").find({}).toArray(function(err, result) {
                if (err) throw err;
                console.log(result);
                res.send(result);
              });

              app.get('/userbyid',(req,res) =>{
                db.collection("users").findOne({})
              }
              )
            
              })

          
    }).catch(console.error)