Function exchange_code 

pub async fn exchange_code(
    http: &Client,
    token_url: &str,
    client_id: &str,
    client_secret: Option<&str>,
    code: &str,
    redirect_uri: &str,
    code_verifier: &str,
) -> Result<TokenSet, TokenError>

Exchanges an authorization code for tokens (PKCE verifier required).

Errors

TokenError on HTTP/protocol failure.