Function is_retryable_error 

pub fn is_retryable_error(error: &Error) -> (bool, Option<u64>)

What: Determine if an error is retryable and extract retry-after information.

Inputs:

• error: The reqwest::Error to classify

Output:

• (bool, Option<u64>) where the bool indicates if the error is retryable, and the Option contains retry-after seconds if available from headers

Details:

• Timeout errors are retryable
• Connection errors are retryable
• HTTP 5xx status codes are retryable
• HTTP 429 (rate limit) is retryable and may include Retry-After header
• HTTP 4xx (except 429) are not retryable (client errors)
• HTTP 3xx are not retryable (redirects handled by reqwest)