How do I set up a Kubernetes review app for an app that has services in multiple projects?

Let’s say I have a PR to phsteve/frontend and a corresponding PR to phsteve/backend and I have my own kubernetes cluster. I’d like to create a review app with those two services and click on a link like and view the website where the frontend talks to a backend service at The examples and documentation I could find seem to be geared towards spinning up a review app for a single project. Is creating a review app that uses multiple projects possible? How would that work?