Improve policy constraint error message

[didierofrivia]

This PR besides aiming to improve the policy constrain error message, introduces a minor refactor. TargetHostnames and ValidateHierarchicalRules were controller methods that didn't need to make any use of the K8s client, thus they were extracted, simplified and unit tested .

The error message now looks like this:

rule host (keystep.arturia.com) does not follow any hierarchical constraints,
for the *v1beta1.RateLimitPolicy to be validated, it must match with at least one 
of the target network hostnames ["*.moog.com", "*.korg.com"]

This new version, besides showing the wrong policy target hostname, it shows the Type of the policy being reconciled and the target network object (HTTPRoute or Gateway) hostnames.

closes #113

Verification Steps

1. Setup your local Kind env with

make local-setup

2. Create a route with the following spec:

 kubectl apply -f - <<EOF
---
apiVersion: gateway.networking.k8s.io/v1alpha2
kind: HTTPRoute
metadata:
  name: toystore
  labels:
    app: toystore
spec:
  parentRefs:
    - name: istio-ingressgateway
      namespace: istio-system
  hostnames: ["*.toystore.com"]
  rules:
    - matches:
        - path:
            type: PathPrefix
            value: "/toy"
          method: GET
      backendRefs:
        - name: toystore
          port: 80
EOF

Note the hostnames value being "*toystore.com"

3. Apply the following RLP:

kubectl apply -f - <<EOF
---
apiVersion: kuadrant.io/v1beta1
kind: RateLimitPolicy
metadata:
  name: toystore
spec:
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: toystore
  rateLimits:
    - rules:
        - hosts: ["*.petstore.com"]
      configurations:
        - actions:
            - generic_key:
                descriptor_key: "limited"
                descriptor_value: "1"
      limits:
        - conditions:
            - "limited == 1"
          maxValue: 5
          seconds: 10
          variables: []
EOF

Note here that the spec.rateLimits[0].hosts value is "*.petstore.com"

4. Once applied, the status of the RLP should show a failed condition with the following message:

kubectl get ratelimitpolicies/toystore -o yaml | yq ".status.conditions[0].message"

rule host (*.petstore.com) does not follow any hierarchical constrains,
for the *v1beta1.RateLimitPolicy to be validated, it must match with 
at least one of the target network hostnames ["*.toystore.com"]

[alexsnaps]

it must match with at least one of the target network hostnames ["*.moog.com", "*.korg.com"]

I think you meant *.moogmusic.com... 😉

[eguzki]

LGTM

There are conflicts to be merged as main has changed since the PR was created

[guicassolato]

Nice catch!

[guicassolato]

👍

[pehala]

The message is certainly better