pub fn on_action_async(
		&self,
		handler: impl (Fn(ActionHandler) -> Box<dyn Future<Output = ActionHandler> + Send + Sync>)
			+ Send
			+ Sync
			+ 'static,
	) -> &Self {
		debug!("Config: on_action_async");
		self.action_handler
			.replace(move |action| ActionReturn::Async(handler(action)));
		self.signal_change()
	}
Set the action handler to a future-returning closure.
crates/lib/src/config.rs