add helm tests

[codefromthecrypt]

helm tests allow you to hit something besides the readiness gate, to know if the chart itself is functional.

https://helm.sh/docs/topics/chart_tests/#example-test

As you'll notice, if you run helm recently, it creates some infrastructure to help with tests, which the current charts don't have (e.g. fullname properties which are substituted by chart-testing for example). It might be worth regenerating the charts here and then after that choosing an endpoint to make sure something really works. For example, in discoveryserver, the /apps endpoint