keystone is not a distribute service an dose not use rabbitmq unless you enable
notifiction with the oslo messaging rabbitmq driver

https://github.com/openstack/keystone/blob/master/keystone/notifications.py
https://docs.openstack.org/keystone/latest/configuration/config-options.html#oslo_messaging_notifications.transport_url

https://docs.openstack.org/keystone/latest/install/keystone-install-rdo.html
https://docs.openstack.org/keystone/latest/install/keystone-install-ubuntu.html

the keystone operator howewver require a rabbit instance

https://github.com/openstack-k8s-operators/keystone-operator/blob/main/api/v1beta1/keystoneapi_types.go#L185-L189

which st the uses for notificaoints

https://github.com/openstack-k8s-operators/keystone-operator/blob/main/templates/keystoneapi/config/keystone.conf#L36-L47
however this is defaultign to the incorrect message bus adn uses the wrong name

the notificaotin message bus shoudl be defied as`NotificationsBusInstance`

	// +kubebuilder:validation:Optional
	// NotificationsBusInstance is the name of the RabbitMqCluster CR to select
	// the Message Bus Service instance used by the Nova top level services and all cells to publish notifications.
	// If undefined, the value will be inherited from OpenStackControlPlane.
	// An empty value "" leaves the notification drivers unconfigured and emitting no notifications at all.
	// Avoid colocating it with RabbitMqClusterName, APIMessageBusInstance or CellMessageBusInstance used for RPC.
	// For particular Nova cells, notifications cannot be disabled, nor configured differently.
	NotificationsBusInstance *string `json:"notificationsBusInstance,omitempty"`

it shoudl not have a default value as notrication shoudl be disabled by default

when its enabeld we use a sepeate rabbitmq instance for it called rabbit-notifications by convention

https://github.com/openstack-k8s-operators/openstack-operator/pull/1591

the rabbitMqClusterName fied was added by
https://github.com/openstack-k8s-operators/keystone-operator/commit/52985536f4624d3a245d63210ab07d9553007cbd

whhich incorectly redused the naem we default to for rpc trafic and make it required instead of optional which is problematic as if notifcaion are not consumed they will pile up indefintly in rabbit unless you configure experiation on the rabbit server for the messages.

thjs seams to have been intorudce for barbican integration

https://github.com/openstack-k8s-operators/barbican-operator/pull/34
however we shoudl nto assuem that barbican is deploy and it shoudl be possibel to deploy without enabling this fucntionaliy.