feat: using node best practices and some improvements

[julianduque]

Major changes:

• Update dependencies to latest (Fastify v5)
• Add real tests
• Improve the invoke.sh script
• Use EcmaScript Modules (no CommonJS)
• Use proper schema validation with Fastify
• Add eslint and prettier
• Add Heroku Button

[Copilot]

Pull Request Overview

This PR modernizes the codebase by moving to ESM, updating to Fastify v5, adding robust schema validation, integrating lint/format tooling, and improving tests and deployment scripts

• Migrate CommonJS to EcmaScript modules across app, routes, plugins, and tests
• Introduce JSON schema validation for new endpoints and expand /accounts test coverage
• Add ESLint/Prettier configuration, update dependencies, and include a Heroku deploy button

Reviewed Changes

Copilot reviewed 17 out of 21 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
package.json	Update metadata, bump dependencies, add lint/format scripts
src/app.js	Migrate to ESM, configure Swagger & Autoload plugins
src/routes/index.js	Convert to ESM, add schema validation for /unitofwork and Data Cloud routes
test/routes/accounts.test.js	Convert tests to ESM and expand /accounts test cases
eslint.config.js	Add ESLint and Prettier integration
README.md	Enhance documentation, add Heroku Deploy button & usage instructions

Comments suppressed due to low confidence (3)

README.md:59

• The README refers to /api-docs, but by default the Swagger UI is exposed at /documentation. Please update the path to match the actual route.

- **GET /api-docs** - Interactive Swagger UI for API documentation

README.md:60

• The docs list /health but the code registers /healthcheck. Align the documentation with the code or adjust the route name for consistency.

- **GET /health** - Health check endpoint

src/routes/index.js:77

• New routes /unitofwork and /handleDataCloudDataChangeEvent have been added, but there are no corresponding tests. Consider adding tests to cover their validation logic and response behavior.

  fastify.post(

[Copilot]

There is a typo in the description: "Sammple" should be "Sample".

Suggested change

	"description": "Heroku AppLink Sammple App with Fastify",
	"description": "Heroku AppLink Sample App with Fastify",

[Copilot]

[nitpick] Returning the reply object without sending any payload can be confusing. You might remove this return or explicitly call reply.send() to clarify the intended behavior.

Suggested change

	return reply;
	reply.send({ success: true });