pub async fn open_connection(
http: &Client,
app_token: &str,
) -> Result<String, String>Expand description
POST apps.connections.open — Authorization: Bearer {app_token}. Returns
the ephemeral Socket Mode WS URL. Must be called before the initial
connect and before every reconnect (spec §2.1) — the URL is single-use
and short-lived; never cache/reuse it.