feat(api): API documentation with Swagger UI

[Nirajn2311]

Checklist:

• I have read and followed the contribution guidelines.
• I have read and followed the how to open a pull request guide.
• My pull request targets the main branch of freeCodeCamp.
• I have tested these changes either locally on my machine, or GitPod.

Closes #49712

To view the documentation, start the server and visit http://localhost:3000/documentation/. One thing to note is even though if you set the session ID the page can't send the request with the cookie for security reasons regarding modifying request headers in browser(More details here swagger-api/swagger-js#1163).

Also do we need the documentation page for production?

[ghost]

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[ShaunSHamilton]

Nice one, Niraj

[ShaunSHamilton]

Also do we need the documentation page for production?

I do not think it matters much, but, if not, then a nice-to-have would be on .dev

[ojeytonwilliams]

Why would we want to enable this in production? I thought it was just a tool to help us develop the api.

[ShaunSHamilton]

Why would we want to enable this in production? I thought it was just a tool to help us develop the api.

We are hoping to provide a REST API for other tools to use. So, our API should be documented somewhere.

[Nirajn2311]

I thought it was just a tool to help us develop the api.

To be clear, irrespective of whether we use the UI in production or development, we can't execute any of the endpoints coz of the restriction I mentioned in the description. It will just be like an API reference page.

[ShaunSHamilton]

Thank you, Niraj

[ojeytonwilliams]

I have reservations about the approach we're taking to env vars, but that's broader than this PR.

Putting them aside for now, this LGTM. Nice work @Nirajn2311 🚀