make reload_handles optional for creating Services

This will be useful for instantiating services in CLI subcommands, which
have different requirements around observeability.

src/cli/serve.rs

@@ -80,7 +80,7 @@ pub(crate) async fn run(args: ServeArgs) -> Result<(), error::ServeCommand> {
             .map_err(Error::DatabaseError)?,
     ));
 
-    Services::build(db, config, reload_handles)
+    Services::build(db, config, Some(reload_handles))
         .map_err(Error::InitializeServices)?
         .install();