Function send_revoke_token_req 

pub async fn send_revoke_token_req(
    req: &RevokeTokenRequest<'_>,
) -> Result<(), Error>

A function that sends an HTTP request to revoke a token (such as an access token or refresh token) using the OAuth2 standard revocation endpoint.

It takes a RevokeTokenRequest struct as input and returns Ok(()) on success, or an Error if the revocation fails.
The implementation uses the reqwest crate internally for HTTP communication.