pub fn register_page_no_state(&self, url: &PathMaybeWithLocale, is_widget: bool) {
        self.page_state_store.set_state_never(url, is_widget);
    }
Registers a page as definitely taking no state, which allows it to be
cached fully, preventing unnecessary network requests. Any future
attempt to set state will lead to silent failures and/or panics.
packages/perseus/src/template/render_ctx.rs