- Updated error handling in `nd_host_scheduler.go`, `nd_host_websocket.go`, `nd_host_artwork.go`, `nd_host_cache.go`, and `nd_host_subsonicapi.go` to convert string errors from responses into Go errors.
- Removed redundant error checks in test data plugins for cleaner code.
- Ensured consistent error handling across all plugins to improve reliability and maintainability.
- Updated the host function signatures in `nd_host_artwork.go`, `nd_host_scheduler.go`, `nd_host_subsonicapi.go`, and `nd_host_websocket.go` to accept a single parameter for JSON requests.
- Introduced structured request and response types for various cache operations in `nd_host_cache.go`.
- Modified cache functions to marshal requests to JSON and unmarshal responses, improving error handling and code clarity.
- Removed redundant memory allocation for string parameters in favor of JSON marshaling.
- Enhanced error handling in WebSocket and cache operations to return structured error responses.
