The Leaky Bucket rate limiter

A few months ago, a customer asked if I could supply a “leaky bucket” rate limiter as part of Sidekiq Enterprise’s rate limiter suite. It took me a while to find the time and energy to work on it (my need to mentally escape the 2020 election eventually did the trick). I went into this process knowing the basics of the leaky bucket algorithm but with no idea how to implement it....