Istio Metrics - Add Custom Dimension for URL pattern

1

I am trying to insert a custom dimension for an istio metric for URL path. I am following the steps here - Istio / Classifying Metrics Based on Request or Response

Specifically, this part, where I can parse the URL and decide the value :

configuration:
                "@type": type.googleapis.com/google.protobuf.StringValue
                value: |
                  {
                    "attributes": [
                      {
                        "output_attribute": "istio_operationId",
                        "match": [
                          {
                            "value": "ListReviews",
                            "condition": "request.url_path == '/reviews' && request.method == 'GET'"
                          },
                          {
                            "value": "GetReview",
                            "condition": "request.url_path.matches('^/reviews/[[:alnum:]]*
```) && request.method == 'GET'"
                          },
                          {
                            "value": "CreateReview",
                            "condition": "request.url_path == '/reviews/' && request.method == 'POST'"
                          }
                        ]
                      }
                    ]
                  }

I want to add a fall-back approach - i.e., if it doesn’t match any URL, then make the value of istio_operationId as the original request.url_path

How can I do that?

I tried adding this as the last condition but it doesn’t work

{
    "value": "request.url_path", //tried without quotes as well
    "condition": "request.url_path.matches('.+$')"
}

Also, is this possible in Lua?