fix: make the error identification middleware optional because of the use case

[supercaracal]

• Add middleware to ensure Router only handles errors for its clients #310
• I doubt whether every user needs the error identification middleware or not. I think our 99% users don't use this library in a nested block against multiple clusters. Also, middlewares are called every time by commands and pipelines. It affects the performance in no small measure.
• The node class doesn't need any dependencies with the middleware. So we should decouple them. The middleware is used by only the router class.