Add rate limiting to requests

[Frewacom]

We should make sure to block malicious users sending too many requests. There are packages available for this, e.g. https://www.npmjs.com/package/rate-limiter-flexible (as per a comment from AdonisJS discord server). Combined with a middleware, this should do just fine.

[McFrappe]

https://github.com/reg2005/adonis-request-throttler might be better suiting