Add alerts for TLS/DNS/Auth/RateLimit policies not targeting Gateways…

[david-martin]

… and HTTPRoutes

Closes #440

To verify:

• Bring up a local cluster as per https://docs.kuadrant.io/getting-started-single-cluster/, using the release-v0.6.2 branch by specifying export KUADRANT_REF=release-v0.6.2
• Bring up an observability stack using these commands from this PR branch
  • ./bin/kustomize build ./config/observability/| docker run --rm -i ryane/kfilt -i kind=CustomResourceDefinition | kubectl apply --server-side -f -
  • ./bin/kustomize build ./config/observability/| docker run --rm -i ryane/kfilt -x kind=CustomResourceDefinition | kubectl apply -f -
• Import the example PrometheusRules resource with the alerting rules
  • kubectl apply -f ./examples/alerts/prometheusrules_policies_missing.yaml
• Create example Gateways, HTTPRotues and policies to verify the alerts behave as expected. It isn't important that the Gateways, HTTPRoutes & policies are actually working, just that they exist in etcd
  • kubectl apply -f https://gist.githubusercontent.com/david-martin/991d76255d90b51860f9ed8724f43983/raw/cc8196e9b9088895054f6f9556929ae10f36554c/alerting_resources.yaml
• Access the Prometheus Alerts tab by using port-forwarding and verify the following alerts are firing
  • kubectl -n monitoring port-forward service/prometheus-k8s 9090:9090
  • open http://127.0.0.1:9090 > Alerts tab
  • There should be a total of 8 Gateway/HTTPRoutes alerts firing (It will take a few minutes for metrics to all be scraped and the pending state to switch to firing). You can check the summary text for each, or run this query from the Graph tab and compare: ALERTS{alertstate="firing",alertname=~"Gateway.*|HTTPRoute.*"}

ALERTS{alertname="GatewayWithoutDnsPolicy", alertstate="firing", container="kube-rbac-proxy-main", customresource_group="gateway.networking.k8s.io", customresource_kind="Gateway", customresource_version="v1beta1", gateway_name="testgw3", gatewayclass_name="test", instance="10.244.0.31:8443", job="kube-state-metrics", name="testgw3", namespace="default", severity="warning"}
1
ALERTS{alertname="GatewayWithoutDnsPolicy", alertstate="firing", container="kube-rbac-proxy-main", customresource_group="gateway.networking.k8s.io", customresource_kind="Gateway", customresource_version="v1beta1", gateway_name="testgw4", gatewayclass_name="test", instance="10.244.0.31:8443", job="kube-state-metrics", name="testgw4", namespace="default", severity="warning"}
1
ALERTS{alertname="GatewayWithoutTlsPolicy", alertstate="firing", container="kube-rbac-proxy-main", customresource_group="gateway.networking.k8s.io", customresource_kind="Gateway", customresource_version="v1beta1", gateway_name="testgw1", gatewayclass_name="test", instance="10.244.0.31:8443", job="kube-state-metrics", name="testgw1", namespace="default", severity="warning"}
1
ALERTS{alertname="GatewayWithoutTlsPolicy", alertstate="firing", container="kube-rbac-proxy-main", customresource_group="gateway.networking.k8s.io", customresource_kind="Gateway", customresource_version="v1beta1", gateway_name="testgw4", gatewayclass_name="test", instance="10.244.0.31:8443", job="kube-state-metrics", name="testgw4", namespace="default", severity="warning"}
1
ALERTS{alertname="HTTPRouteWithoutAuthPolicy", alertstate="firing", container="kube-rbac-proxy-main", customresource_group="gateway.networking.k8s.io", customresource_kind="HTTPRoute", customresource_version="v1beta1", httproute_name="testhttproute1", instance="10.244.0.31:8443", job="kube-state-metrics", name="testhttproute1", namespace="default", severity="warning"}
1
ALERTS{alertname="HTTPRouteWithoutAuthPolicy", alertstate="firing", container="kube-rbac-proxy-main", customresource_group="gateway.networking.k8s.io", customresource_kind="HTTPRoute", customresource_version="v1beta1", httproute_name="testhttproute4", instance="10.244.0.31:8443", job="kube-state-metrics", name="testhttproute4", namespace="default", severity="warning"}
1
ALERTS{alertname="HTTPRouteWithoutRateLimitPolicy", alertstate="firing", container="kube-rbac-proxy-main", customresource_group="gateway.networking.k8s.io", customresource_kind="HTTPRoute", customresource_version="v1beta1", httproute_name="testhttproute3", instance="10.244.0.31:8443", job="kube-state-metrics", name="testhttproute3", namespace="default", severity="warning"}
1
ALERTS{alertname="HTTPRouteWithoutRateLimitPolicy", alertstate="firing", container="kube-rbac-proxy-main", customresource_group="gateway.networking.k8s.io", customresource_kind="HTTPRoute", customresource_version="v1beta1", httproute_name="testhttproute4", instance="10.244.0.31:8443", job="kube-state-metrics", name="testhttproute4", namespace="default", severity="warning"}