Add Rust backend with auth routes

[chrisgzf]

In preparation for our future reviews system that makes use of our own database (so that we can get rid of Disqus - they have been injecting ads into our site, bleh), this is a bootstrapped new 🦀Rust🦀 backend.

What's done:

• NUS auth
  • to test, after running backend, visit: http://localhost:3000/v1/auth/login?callback=http://localhost:3000/v1/auth/user
• Setting up of routes

What's next:

• Setting up of the DB (I'm still deciding between Postgres or Clickhouse)
• Migrating disqus comments to the DB
• GET api/v1/reviews/:course_id -> Vec<Reviews>
• POST api/v1/reviews/:course_id: should create review
• PUT api/v1/reviews/:course_id/:review_id: should edit review
• DELETE api/v1/reviews/:course_id/:review_id: should delete review

🦀🦀🦀

[vercel[bot]]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Updated (UTC)
nusmods-export	✅ Ready (Inspect)	Visit Preview	Dec 17, 2023 5:24pm
nusmods-website	✅ Ready (Inspect)	Visit Preview	Dec 17, 2023 5:24pm

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (17c4bc3) 53.24% compared to head (ee789f6) 53.24%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3645 +/- ## ======================================= Coverage 53.24% 53.24% ======================================= Files 271 271 Lines 5862 5862 Branches 1396 1396 ======================================= Hits 3121 3121 Misses 2741 2741 ```

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