Function send_or_edit 

pub async fn send_or_edit(
    http: &Client,
    token: &str,
    chat_id: i64,
    text: &str,
    edit_message_id: Option<i64>,
) -> Result<Message, TelegramApiError>

Dispatches to send_message or edit_message_text depending on whether edit_message_id is set (spec §2.3 — streaming-output simulation).