Function init_and_spawn_megaphone_updater

pub async fn init_and_spawn_megaphone_updater(
    broadcaster: &Arc<RwLock<BroadcastChangeTracker>>,
    http: &Client,
    metrics: &Arc<StatsdClient>,
    url: &str,
    token: &str,
    poll_interval: Duration,
) -> Result<()>

Initialize the BroadcastChangeTracker

Immediately populates it with the current Broadcasts polled from the Megaphone service, then spawns a background task to periodically refresh it