Looking at the docs, I think what changed is that `throttled_responder` gets the request as an argument instead of the `env`? And has the same return type for the lambda as before?
So uhhh I don't remember how to test this, but uhh it's not crashing when the server starts anymore, and I feel like the most likely problem here would be that you get a 500 instead of a useful response in the rate limit case, so like. ehh I'll just leave it be!
