feat: add GET /users/{id} endpoint with validation and 404 handling

[triantafillos]

This pull request adds a new /users/:id API endpoint to server.js for retrieving user information by ID, including proper error handling for invalid or missing users. It also updates the server startup logs to mention the new endpoint.

New API endpoint and logging:

• Added a mock users database and a /users/:id GET endpoint that returns user data for a given ID, with validation for numeric IDs and 404 handling if the user is not found.
• Updated the server startup message to include the /users/[id] endpoint.

[Copilot]

Pull Request Overview

This PR adds a new REST API endpoint for retrieving users by ID, including proper error handling for invalid inputs and non-existent users.

Key changes:

• Added a mock users database with three sample users
• Implemented GET /users/:id endpoint with input validation and 404 handling
• Added console log for the new endpoint on server startup

Comments suppressed due to low confidence (1)

server.js:1

• The endpoint exposes user email addresses in the response. Consider whether this is intentional or if sensitive user data should be filtered from API responses to prevent data exposure.

const express = require('express');

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[Copilot]

The validation for isNaN(userId) does not handle negative numbers or zero, which may not be valid user IDs based on the current data model (IDs start at 1). Consider adding validation to reject non-positive integers: if (isNaN(userId) || userId <= 0) with an appropriate error message.

Suggested change

	// Validate that id is a number
	if (isNaN(userId)) {
	return res.status(400).json({
	error: 'Invalid user ID',
	message: 'User ID must be a number',
	// Validate that id is a positive integer
	if (isNaN(userId) || userId <= 0) {
	return res.status(400).json({
	error: 'Invalid user ID',
	message: 'User ID must be a positive integer',