Function run_startup_challenge_client 

async fn run_startup_challenge_client(
    runtime: AuthChallengeRuntime,
    snapshots: Receiver<Option<AuthChallengeSnapshot>>,
    verify_cb: Option<VerifyCodeCallback>,
    picture_prompt: Option<Arc<dyn Fn() -> Option<String> + Send + Sync>>,
    allow_external_verification: bool,
) -> Result<()>