What?

Whenever an incompatible OpenShift Service Mesh (OSSM) Subscription resource is present, we will fail to provision Gateway API and report the problem. This epic specifically targets compatibility issues related to the required Istio control plane version (as defined by `Istio` custom resource).

Why?

Users might have deployed OSSM operator prior to upgrading to a version where the CIO provides Gateway API support via OSSM. The pre-existing OSSM operator installation might not support the Istio control plane version required by CIO. We can't automatically resolve this problem at this time in a way that's safe for previous OSSM deployments, so we must bail.

How?

The CIO logic should follow these guidelines:

IF a compatible (installedCSV == expected CSV) Subscription is present, AND a supported `GatewayClass` resource is created, BUT the installed OSSM operator does not support the expected Istio control plane version:
1. Fail to create a OSSM 3.x Subscription (having 2.x and 3.x coexisting is not supported).
2. Stop trying provision the Gateway API resources in any way.
3. Set a Degraded status to True on the ingress cluster operator which indicates the problem until either the GatewayClass or a conflicting subscription is removed.
4. Do any other reporting/logging that seems appropriate for the situation (e.g. warning messages similar to conflicting subscription).

Notes

• Conflicting subscriptions are handled by "Detect conflicting OSSM subscriptions for Gateway API" epic and reported as Degraded=True for the ingress cluster operator.