Function sign_message_with_api_key 

pub fn sign_message_with_api_key(
    token: &str,
    wallet_name_or_id: &str,
    chain: &Chain,
    msg_bytes: &[u8],
    index: Option<u32>,
    vault_path: Option<&Path>,
) -> Result<SignResult, OwsLibError>

Sign a message using an API token (agent mode).