Context:

Following changes for the Global Hub feature to make alermanager secret name unique by hub cluster, the generated name becomes too long in some cases where the hub domain is long. Cf https://redhat-internal.slack.com/archives/CUU609ZQC/p1765941596137909

As a result, the injected secret name into the CMO configuration is too long as the operator adds a 'secret-' prefix for the volume names generated from the secret names, pushing the total length past the Kubernetes limit. And the statefulset is not able to start. Breaking the CMO monitoring stack.

The only fallback is to disable alert forwarding so that the CMO configuration is not updated with the secret name.

Acceptance:

Another suffix is used to have the alermanager secret name unique by hub cluster and shorter than 55 characters. Lower if possible. 
As suffix, we can use the beginning of the hub cluster ID or a short hash of the domain.