Your company hosts a legacy web application behind an Azure Application Gateway v2. The application stores session state locally in memory on each backend VM rather than in a shared store. Users report that they are intermittently logged out and their shopping carts are lost as they navigate the site. You confirm the backend pool has three healthy VMs and that health probes are passing. You must ensure a user's requests are consistently sent to the same backend VM for the duration of their session, with minimal changes to the application. What should you configure?