slingshot: add configurable port and host to slingshot, configurable port to metrics

slingshot/src/main.rs

···
     /// disk cache size in GB
     #[arg(long, default_value_t = 1)]
     cache_disk_gb: usize,
+    /// port for HTTP server (when not using --domain)
+    #[arg(long, default_value_t = 3000)]
+    port: u16,
+    /// port for metrics/prometheus server
+    #[arg(long, default_value_t = 8765)]
+    metrics_port: u16,
     /// the domain pointing to this server
     ///
     /// if present:
···
 
     let args = Args::parse();
 
-    if let Err(e) = install_metrics_server() {
+    if let Err(e) = install_metrics_server(args.metrics_port) {
         log::error!("failed to install metrics server: {e:?}");
     } else {
-        log::info!("metrics listening at http://0.0.0.0:8765");
+        log::info!("metrics listening at http://0.0.0.0:{}", args.metrics_port);
     }
 
     std::fs::create_dir_all(&args.cache_dir).map_err(|e| {
···
             args.domain,
             args.acme_contact,
             args.certs,
+            args.port,
             server_shutdown,
         )
         .await?;
···
     Ok(())
 }
 
-fn install_metrics_server() -> Result<(), metrics_exporter_prometheus::BuildError> {
+fn install_metrics_server(port: u16) -> Result<(), metrics_exporter_prometheus::BuildError> {
     log::info!("installing metrics server...");
     let host = [0, 0, 0, 0];
-    let port = 8765;
     PrometheusBuilder::new()
         .set_quantiles(&[0.5, 0.9, 0.99, 1.0])?
         .set_bucket_duration(std::time::Duration::from_secs(300))?

slingshot/src/server.rs

···
     domain: Option<String>,
     acme_contact: Option<String>,
     certs: Option<PathBuf>,
+    port: u16,
     shutdown: CancellationToken,
 ) -> Result<(), ServerError> {
     let repo = Arc::new(repo);
···
         )
         .await
     } else {
-        run(TcpListener::bind("127.0.0.1:3000"), app, shutdown).await
+        run(
+            TcpListener::bind(format!("127.0.0.1:{port}")),
+            app,
+            shutdown,
+        )
+        .await
     }
 }