It is possible to set forceBackendUrlToFrontendUrl as an environment variable in Kubernetes?

My problem is that the backend communication from pod to pod is over unencrypted HTTP. Keycloak (frontend) is only reachable over HTTPS.

The JWT has the "iss" claim https://......, and the service calls Keycloak to check this token. Keycloak says the token is invalid because the "issues" is invalid - and yes, it is right, https is not http.

I think i must set the variable forceBackendUrlToFrontendUrl from the Keycloak documentation, but I have no idea how I can set this in Kubernetes.