Function extract_header_request_id 

pub fn extract_header_request_id(
    headers: &HeaderMap,
) -> Result<Option<&str>, Error>

Extract a request ID from request fields.

X-Request-Id takes precedence over Request-Id; the fallback is inspected only when X-Request-Id is absent. If both are absent, this function returns None. The selected value is returned unchanged, so an empty field produces Some(""). A selected field that occurs more than once or is not text produces an error that does not contain the field value. This function does not generate, validate, authenticate, or log an identifier.