429 errors should get a http header in the response with timestamp for the next time slot

[mgerhardy]

currently i have to wait a random time and retry - it would be better to know how long I have to wait before issuing the next request. This would also again reduce the traffic on your api - because there would be less false-attempts that would still hit the rate limit.

There should be Retry-After in the header.

https://www.rfc-editor.org/rfc/rfc9110.html#name-retry-after