Function serve_ingestion 

pub async fn serve_ingestion(
    listen_addr: SocketAddr,
    lake: DataLakeConnection,
    auth_provider: Option<Arc<dyn AuthProvider>>,
    shutdown: impl Future<Output = ()> + Send + 'static,
    grace: Duration,
) -> Result<()>

Assemble and serve the HTTP ingestion endpoint.

Binds listen_addr, wires the ingestion routes + OTLP routes, applies the supplied auth_provider (or runs open when None), and shuts down gracefully when shutdown resolves.