.github: add schema validation for files used for matrix generation

To prevent developer mistakes we can make use of a schema to perform the
validation of these files.

Suggested-by: Maciej Kwiek <maciej@isovalent.com>
Signed-off-by: André Martins <andre@cilium.io>

.github/actions/ginkgo/focus-schema.yaml

@@ -0,0 +1,11 @@
+focus: list(str())
+include: list(include('includeItem'))
+exclude: list(include('excludeItem'))
+---
+includeItem:
+  focus: str()
+  cliFocus: str()
+  cliSkip: str(required=False)
+excludeItem:
+  k8s-version: str()
+  focus: str()

.github/actions/ginkgo/k8s-versions-schema.yaml

@@ -0,0 +1,7 @@
+include: list(include('includeItem'))
+---
+includeItem:
+  k8s-version: str()
+  ip-family: str()
+  kube-image: str()
+  kernel: str()

.github/actions/ginkgo/prs-schema.yaml

@@ -0,0 +1 @@
+k8s-version: list(str())

.github/actions/ginkgo/scheduled-schema.yaml

@@ -0,0 +1 @@
+k8s-version: list(str())

.github/workflows/lint-workflows.yaml

@@ -135,3 +135,25 @@ jobs:
             echo "Please fix the comments from .github/workflows/conformance-runtime.yaml accordingly"
             exit 1
           fi
+
+  ginkgo-schema-validation:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/setup-python@bd6b4b6205c4dbad673328db7b31b7fab9e241c0 # v4.6.1
+        with:
+          python-version: '3.10'
+      - run: pip install yamale
+      - name: Checkout code
+        uses: actions/checkout@8e5e7e5ab8b370d6c329ec480221332ada57f0ab # v3.5.2
+        with:
+          persist-credentials: false
+          # hard-code the path instead of using ${{ github.repository }} to make sure it works for forked repo as well
+          path: src/github.com/cilium/cilium
+
+      - name: Validate schema of ginkgo action files
+        shell: bash
+        run: |
+          cd src/github.com/cilium/cilium/.github/actions/ginkgo/
+          for type in focus k8s-versions prs scheduled; do
+            yamale -s ${type}-schema.yaml *-${type}.yaml;
+          done