It would make sense to include the rate limit info in the ErrorResponse

[Ruud-cb]

...Because when a exception occurs with a 429 ToManyRequests, the ErrorResponse exception does not contain info about the reset-datetime or how many seconds I need to wait.
Such info now needs to be cached with OK requests.

Please call the ProcessRateLimits and include it in the constructor of ErrorResponse at the following line:

PexelsDotNetSDK/PexelsClient.cs

Line 335 in 9271072

throw new ErrorResponse(response.StatusCode, responseBody);

[Ruud-cb]

Seems like there is also a difference between to many requests in a short period of time, and actually reaching the monthly limit.
In both cases, a reset-time-date would be the best option. That can either be a in a few days time (when the monthly limit is reached) or in a few seconds.