Function handle_all_books_request 

pub async fn handle_all_books_request<B>(
    req: Request<B>,
    static_: Static,
    index_html: Arc<String>,
) -> Result<Response<BoxBody<Bytes, Error>>, Error>

handle request for the --all index page.

Serves the provided index_html for the root path /, and delegates everything else to the underlying static file server.