Faster feedback on helm chart issues/formatting standards

Is your feature request related to a problem? Please describe.

Currently our helm charts are "tested" at deploy time only, and excluded from the minimal yamllint checks we do. It would be nice to have a fast failure on the helm charts if they are malformed, and also some standard linting against them.

Describe the solution you'd like

A few suggestions to run in CI/locally, tied to the current lint tasks likely:

• helm lint --strict src/**/chart: this is very basic linting, but would catch small things quickly
• helm template <chart>: Good smoke test that the chart will template successfully with default values, but would not validate edge cases with certain values configuration
• helm template <chart> + yamllint against the templated files: This would be nice to catch weird/wrong formatting, a bit more advanced and longer to run

Describe alternatives you've considered

I think there are things that might be too far for "smoke testing", such as using https://github.com/helm/chart-testing/tree/main , but could be worth exploring for some of the specific charts we maintain (keycloak/authservice?).

Additional context

This was spawned out of attempting to use yamllint against charts and hitting issues due to the helm template formatting. It would be nice to havelinting/validation run before our longer CI kicks off.