ACM-26604 Observability alertmanager secret rename

Fixes: https://issues.redhat.com/browse/ACM-26604

Signed-off-by: Jacob Baungard Hansen <jacobbaungard@redhat.com>

Author: jacobbaungard

release_notes/known_issues_observability.adoc

@@ -7,6 +7,12 @@ For your {ocp} cluster, see link:https://docs.redhat.com/en/documentation/opensh
 
 For more about deprecations and removals, see xref:../release_notes/acm_deprecate_remove.adoc#deprecations-removals-acm[Deprecations and removals for {acm-short}]. 
 
+[#alertmanager-accessor-change]
+== Manually configured alert forwarding not working after updating to {acm-short} 2.15
+In {acm-short} 2.15 the name of the `observability-alertmanager-accessor` secret was changed to include a postfix of the hub cluster name, for example: `observability-alertmanager-accessor-hub1-region1`. On systems where the automatic handling for alert-forwarding config has been disabled with the annotation: `mco-disable-alerting: true` on the `MultiClusterObservability` CR, and alert forwarding has been manually configured to forward alerts to the hub (with a policy, GitOps or by other methods), this config needs updating.
+
+For platform alerts the `cluster-monitoring-config` configmap in namespace `openshift-monitoring` should be updated and for user-workload alerts the configmap `user-workload-monitoring-config` in namespace: ` openshift-user-workload-monitoring` should be updated. The exact secret name can be found by viewing the secrets in the mentioned namespaces.
+
 [#retention-change]
 == Retention change causes data loss