"Clean Architecture" design pattern with Node.JS and MongoDB

After some time poorly designing my web applications' backends (mixing database calls with the controller, etc.), I have decided to try the "Clean Architecture" approach.

In this example I have a REST api users which allows you to get a list of all users in MongoDB and to put a user inside the database.

Please, any suggestion on how I can make it better organized would be awesome.

app.js

const express = require("express");
const bodyParser = require("body-parser");
const config = require("./config.js");

const Routes = require("./src/routes.js");
const Database = require("./src/database.js");

const app = express();
app.use(bodyParser.json());

const PORT = config.PORT;

app.use("/api/", Routes());

new Database(config.MONGODB_URI) // connects to the database using MONGODB cluster URL
.then(() => {
    app.listen(config.PORT, () => {
        console.log(`Server running on port ${config.PORT}`);
    }); 
})
.catch((err) => console.error(err));

/src/routes.js

const express = require("express");

const usersRouter = require("./user/routes.js");


const Routes = (dependencies) =>
{
    const router = express.Router();
    router.use("/users", usersRouter(dependencies));
    return router;
};

module.exports = Routes;

/src/database.js

const mongoose = require("mongoose");

module.exports = class Database{
    constructor(connection){
        this.connection = connection;

        return mongoose.connect(this.connection, {
            useNewUrlParser: true,
            useUnifiedTopology: true
        });
    }
};

src/user/routes.js

const express = require("express");
const UserController = require("./controller.js");
const UserModal = require("./data_access/modal.js");
const UserRepository = require("./repository.js");

const userRoutes = () => {
    const modal = UserModal; // pretty much the User modal/document
    const repository = new UserRepository(modal); // talks to the db
    const router = express.Router();
    const controller = UserController(repository); // handles request, sends repository to services

    router.route('/')
    .get(controller.getUsers)
    .post(controller.addUser);

    return router;
};

module.exports = userRoutes;

src/user/repository.js

module.exports = class UserRepository{
    constructor(model){
        this.model = model;
    }

    create(user){
        return new Promise((resolve, reject) =>{
            this.model(user).save();
            resolve(user);
        });
    }

    getByEmail(email){
        return new Promise((resolve, reject) =>{
            this.model.find({email: email})
            .then((user) => resolve(user[0]));
        });
    }

    getByUsername(username){
        return new Promise((resolve, reject) =>{
            this.model.find({username: username})
            .then((user) => resolve(user[0]));
        });
    }

    getAll(){
        return new Promise((resolve, reject) => {
            const students = this.model.find({});
            resolve(students);
        });
    }
};

src/user/controller.js

const GetUsers = require("./services/get_users.js");
const AddUser = require("./services/add_user.js");

module.exports = (repository) => {
    const getUsers = (req, res) => {
        GetUsers(repository)
        .execute()
        .then((result) => res.sendStatus(200).json(result))
        .catch((err) => console.error(err));
    };

    const addUser = (req, res) => {
        const { username, email } = req.body;

        AddUser(repository)
        .execute(username, email)
        .then((result) => res.send(200))
        .catch((err) => {
            res.send(403);
            console.error(err);
        });
    };

    return {
        getUsers,
        addUser
    };
};

/src/user/services/add_user.js

module.exports = (repository) => 
{
    async function execute(username, email){
        return Promise.all([repository.getByUsername(username), repository.getByEmail(email)])
        .then((user) => {
            if(user[0]){
                return Promise.reject("username already taken!");
            }
            else if(user[1]){
                return Promise.reject("email already taken!");
            }
            else{
                repository.create({username: username, email: email});

                return Promise.resolve("all good!");
            }
        });
    }

    return {execute};
};

src/user/services/get_user.js

module.exports = (repository) => 
{
    async function execute(){
        const users = repository.getAll();
        return new Promise((resolve, reject) => resolve(users));
    }

    return {execute};
};

src/user/data_access/schema.js (entities)

const mongoose = require("mongoose");

module.exports = new mongoose.Schema(
{
    username: {
        type: String
    },
    email: {
        type: String
    },
    password_hash: {
        type: String
    }
});

src/user/data_access/model.js (entities)

const mongoose = require("mongoose");
const userSchema = require("./schema.js");

const UserModal = mongoose.model("User", userSchema);

module.exports = UserModal;