How to set a ConsistentHashLB policy on Istio based on the URL id?

In the context of improving an API on Kubernetes, I am considering using a distributed hash table. My API always receives requests to an URL with this scheme:

Reading the documentation of Istio, it seems pretty direct and easy to get what I want. Indeed, Istio handles a load balancing scheme called ConsistentHashLB. I such a scheme, the service destination is chosen according to a hash computed from several possible fields: HTTP header name, cookie, source IP, and an HTTP query parameter name.

In my case, I would need to compute the hash according to the id associated with the request.

That said, I dare some questions:

  1. Given an URL, how could I get its string?

  2. If I get the full URL, how could I get the suffix (the id part

  3. Could I use the field httpQueryParameterName for extracting the id?

  4. If not, how I could add an HTTP header so that later I use httpHeaderName and voila?

In the paper, the solution seems pretty straightforward, but the lack of examples makes hard things.

Thank you very much in advance