Improved Error Handling for Unimplemented Backend Recipe

[anku255]

Currently, when an unimplemented recipeId (rid) is passed in the header, the middleware doesn't handle the request. It results in a generic 404 error, providing limited information.

Proposal: Enhance the middleware to return a more informative error message when a valid recipeId is passed but not implemented by the backend. The updated response will include the message: ${recipeId} is not implemented by the backend