enhancement(ci): Validate Helm chart in CI (#1957)

#### Description

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Adds helm charts validation to the CI.

Fixes #<!-- Link the relevant issue here -->
#1549

#### Checklist 

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- [x] The PR title has the correct prefix 
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---------

Signed-off-by: Piotr Solarczyk <psolarcz@cisco.com>

.github/workflows/pr-test.yaml

@@ -236,3 +236,19 @@ jobs:
         with:
           against: https://github.com/cerbos/cerbos.git#tag=${{ steps.latest-release.outputs.tag }}
           since: https://github.com/cerbos/cerbos.git#branch=main
+
+  test-helm:
+    needs: changes
+    if: ${{ needs.changes.outputs.code == 'true' }}
+    name: Helm test
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-go@v4
+        with:
+          go-version: '>=1.21'
+
+      - name: Test Helm chart
+        run: ./deploy/charts/validate.sh

deploy/charts/validate.sh

@@ -11,6 +11,9 @@ MIN_KUBE_VERSION="1.23.0"
 if ! command -v kubeconform &> /dev/null; then
     go install github.com/yannh/kubeconform/cmd/kubeconform@latest
 fi
+if ! command -v pluto &> /dev/null; then
+    go install github.com/fairwindsops/pluto@latest 
+fi
 
 for VALUES_FILE in "${CHART_DIR}"/values*; do
     echo "Checking $VALUES_FILE"
@@ -19,6 +22,7 @@ for VALUES_FILE in "${CHART_DIR}"/values*; do
         -schema-location default \
         -schema-location 'https://raw.githubusercontent.com/datreeio/CRDs-catalog/main/{{.Group}}/{{.ResourceKind}}_{{.ResourceAPIVersion}}.json' \
         -summary
+    helm template cerbos-test "$CHART_DIR" --values="$VALUES_FILE" --kube-version="$MIN_KUBE_VERSION" | pluto detect - --target-version v"$MIN_KUBE_VERSION"
     echo " "
 done