## Summary
- Upgrades cert-manager from v1.19.2 to v1.20.2
- Enables `enableGatewayAPI: true` via the `ControllerConfiguration` config block
## Why
cert-manager's Gateway API integration was not enabled. Without it, `cert-manager.io/*` annotations on Gateway resources are ignored and no certificates are issued. This is required for the consul and vault PRs (#148, #149) to have their TLS certs automatically provisioned from their Gateway annotations.
In v1.20.2, `ExperimentalGatewayAPISupport` is BETA and defaults to true — enabling `enableGatewayAPI` in the controller config activates the gateway-shim controller.
## Test plan
- [ ] cert-manager rolls out cleanly (v1.20.2 pods become Ready)
- [ ] After rollout, existing Gateway-annotated services (artifactapi, puppet, litellm) retain valid certs
- [ ] New Gateway resources with `cert-manager.io/cluster-issuer` annotations trigger Certificate creation
Reviewed-on: #150