Add alert for unlabelled tenant namespaces

[simu]

Context

We currently deploy the following alerting rule through the hierarchy:

parameters:
  openshift4_monitoring:
    rules:
      appuio-cloud:
        alert:UnlabelledTenantNamespace:
          expr: 'sum by (namespace) (kube_namespace_labels{namespace!~"default|cilium|syn.*|openshift.*|appuio-.*|kube-.*",label_appuio_io_organization=""}) > 0'
          for: "1m"
          annotations:
            message: |-
              Tenant namespace {{ $labels.namespace }} doesn't have the `appuio.io/organization` label.

Note that the namespace regex matches the list of reserved namespaces in the component defaults. We should configure this alerting rule through the component, and exclude namespaces based on the contents of parameter reservedNamespaces, cf.

component-appuio-cloud/class/defaults.yml

Lines 138 to 143 in 428ed1d

	reservedNamespaces:
	kubernetes: ["default", "kube-*"]
	openshift: openshift-*
	projectsyn: syn-*
	appuio: appuio-*
	cilium: cilium*

Alternatives

Keep the config in the hiearchy