Add Kubeval checks to the CI pipeline

**Is your feature request related to a problem? Please describe.**
No. I just noticed that the CI pipeline does not perform a Kubeval check.

**Description**
Kubeval can be used with something in the lines of:

```
$ helm template "${CHART_DIR}" | ./kubeval --strict --ignore-missing-schemas --kubernetes-version "${KUBERNETES_VERSION#v}" --schema-location "${SCHEMA_LOCATION}"
```

My local linting/checking pipeline complained about:

```
The document vault-helm/templates/server-headless-service.yaml contains an invalid Service
---> metadata.annotations: Invalid type. Expected: object, given: null
The document vault-helm/templates/server-service.yaml contains an invalid Service
---> metadata.annotations: Invalid type. Expected: object, given: null
```

Start by locating the repository's CI pipeline and the Helm chart templates named in the report, then run the shown helm template and Kubeval command against the chart. Add the check so CI validates rendered manifests with the stated strict, schema, and Kubernetes-version options, and confirm the pipeline reports invalid manifests while accepting valid ones.

Written by the indexing model from the issue text.