feature: custom 429 per limit

[euri10]

so far we can have a custom 429 but only one, what would be cool is to have a custom 429 per limit, e.g.

429 "you reached your daily limit" if the daily limit is passed

however I wonder at what level this kind of config would make sense

[abersheeran]

Because 429 handler is a complete ASGI application. So as long as the current limiting information can be passed to it, a highly customized response can be achieved.