Function verify_solution 

pub fn verify_solution(
    payload: &Payload,
    hmac_key: &str,
    check_expire: bool,
) -> Result<(), Error>

Verifies the solution provided by the client.

Arguments

• payload: The payload to verify.
• hmac_key: The HMAC key used for verification.
• check_expire: Whether to check if the challenge has expired.

returns: Result<(), Error> Whether the solution is valid.