Add rate limiting

[ZacharyDavidSaunders]

The API needs rate limiting (see ZacharyDavidSaunders/pseudoname#9).

https://www.npmjs.com/package/express-rate-limit may be a good option.

[ZacharyDavidSaunders]

The rate-limiting functionality has been added to the "rate-limiting" branch. I'm going to explore the possibility of adding tests but I don't want the tests to take 30 minutes to finish (the current cooldown period for each route). With that said however, there is value adding rate-limiting tests. 🤔

[ZacharyDavidSaunders]

I've looked into this a bit further. The challenge is that each route test and each middleware test counts towards the rate-limited number (permittedRequestsPerInterval in the code). I could make the tests talk to each other and keep a collective count of how many requests have been made for each route, but that still doesn't address the issue of waiting until the delay has finished. With all of this in mind, I don't think tests are worth the added complexity in this case. I'm going omit tests and merge this change into the "API Rebuild" branch shortly.

[ZacharyDavidSaunders]

Merged (#23) 😄