Disable concurrent ActionCable workers

Otherwise, the ACE events we receive might not be forwarded in the same order. For now, I am not aware of another mechanism to ensure the correct ordering, so that I decided to use this approach for now. Might need to be improved later.

config/application.rb

@@ -60,5 +60,8 @@ module CodeOcean
 
     # Extract Sentry-related parameters from WebSocket connection
     config.middleware.insert_before 0, Middleware::WebSocketSentryHeaders
+
+    # Disable concurrent ActionCable workers to ensure ACE change events keep their order
+    config.action_cable.worker_pool_size = 1
   end
 end