CAPO currently only supports ExternalNetworkID, while the install-config only accepts a external network name.

https://github.com/kubernetes-sigs/cluster-api-provider-openstack/blob/main/api/v1alpha7/openstackcluster_types.go#L71
https://github.com/openshift/installer/blob/master/pkg/types/openstack/platform.go#L26

This is critical for integration with the installer work. Because the CAPO manifests will be generated before the server group is created, it is not possible to specify the external network UUID in the manifests. CAPO requires an external network to be specified, so without this change it is not possible to use CAPO.