feat(router): added a simple wrapper around background tasks

[dotansimha]

Can be easily used like that to create background tasks that are also linked to the lifetime of the server:

pub struct TestTask;

#[async_trait]
impl BackgroundTask for TestTask {
    fn id(&self) -> &str {
        "TestTask"
    }

    async fn run(&self, token: CancellationToken) {
        let mut interval = tokio::time::interval(Duration::from_secs(3));
        loop {
            tokio::select! {
                _ = interval.tick() => { println!("running"); }
                _ = token.cancelled() => { println!("Shutting down."); return; }
            }
        }
    }
}

// then later
manager.register_task(TestTask);

[gemini-code-assist]

Summary of Changes

Hello @dotansimha, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a new framework for managing background tasks within the router application. It provides a BackgroundTask trait and a BackgroundTasksManager to register and oversee long-running asynchronous operations, ensuring they are properly initialized and gracefully terminated in sync with the server's lifecycle. This enhancement improves the robustness and maintainability of background processes.

Highlights

• New Background Task System: Introduced a new background_tasks module that provides a structured way to define and manage asynchronous background operations within the router.
• Graceful Shutdown: Implemented a BackgroundTasksManager that uses tokio-util's CancellationToken to ensure all registered background tasks are gracefully shut down when the server stops.
• Dependency Update: Added tokio-util as a new dependency to facilitate the implementation of cancellation tokens for background tasks.

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[gemini-code-assist]

Code Review

This pull request introduces a simple and effective manager for background tasks, which is a great addition for handling long-running processes tied to the server's lifecycle. The use of CancellationToken for graceful shutdown is well-implemented. My review includes a few suggestions to enhance robustness by handling task panics, improve logging consistency, and correct a minor typo.

[gemini-code-assist]

There are a couple of improvements that can be made here:

1. Handle Task Panics: The result of join_all is currently ignored. If a background task panics, it will result in a JoinError which will be silently swallowed. It's important to handle these results and log any panics to aid in debugging.
2. Consistent Logging: The println! macro is used, but the rest of the project uses the tracing crate. For consistency and to benefit from structured logging, it's better to use info!.

This suggestion addresses both points.

        let join_results = join_all(self.task_handles).await;
        for result in join_results {
            if let Err(err) = result {
                error!("A background task panicked during shutdown: {:?}", err);
            }
        }

        info!("all background tasks have been shut down gracefully.");

[gemini-code-assist]

There's a typo in the log message. "clearning" should be "cleaning".

Suggested change

	info!("server stopped, clearning background tasks");
	info!("server stopped, cleaning background tasks");

[kamilkisiela]

Let's wait with merging this PR until we actually use it for something