Allow existing secret to be used in helm chart #59
Description
Currently there appears to be no way to set an existing secret as the source for clickhouse, postgres, redis, secrets and others.
A lot of people who use helm charts use them as part of a gitops workflow where the values files are stored in a repository and the secrets are stored elsewhere.
It would be great if the chart could support specifying an existing secret for any secret values instead of requiring them to be stored within the values file itself, since storing them in the values file (which may end up in source control) is not a good security practice.