Function rest_availability_service_stream_headers 

async fn rest_availability_service_stream_headers<S>(
    __arg0: State<Arc<S>>,
    headers: HeaderMap,
    __arg2: Query<StreamHeadersRequest>,
) -> Result<Sse<impl Stream<Item = Result<Event, Infallible>>>, RestError>
where
    S: AvailabilityService + Send + Sync + 'static,

StreamHeaders - SSE streaming endpoint.

GET /v2/availability/stream/headers → text/event-stream