Refactor StateManager into the ProcessingEngine

And add some tests

Co-authored-by: Ben Lambert <ben@blam.sh>
Signed-off-by: Johan Haals <johan.haals@gmail.com>

packages/backend/src/plugins/catalog.ts

@@ -42,7 +42,7 @@ export default async function createPlugin(
     } = await builder.build();
 
     // TODO(jhaals): run and manage in background.
-    processingEngine.start();
+    await processingEngine.start();
 
     return await createRouter({
       entitiesCatalog,