OpenShift deployment testing

[willdollman]

Emulate some OpenShift behaviour with our helm charts to make testing using k8s easier:

• Use high uid/gids
• Add user to the root group
• Set fsGroup 0 to ensure files are owned by root group
• Set fsGroupChangePolicy: always

Running this locally with helm works fine (older version from my shell history, but should also work on newer instances):

$ helm upgrade --install sourcegraph --version 5.6.2535 ./ --values ../../override.yaml --namespace default

This PR is just for sharing helm charts for OpenShift testing - it shouldn't be merged

Issues

• This relies on created files' group permissions matching owner permissions. If files are created with 744 or 755, then the user will lack execute/write permissions on the file after a pod restart. I've checked a few containers and quite a few do this:
  • Gitserver writes files with 755
  • Redis writes with 755

Checklist

• Follow the manual testing process
• Update changelog
• Update Kubernetes update doc

Test plan