[Enhancement][opensearch-dashboard] put opensearch_dashboards.yml into a Secret

[domruf]

Is your feature request related to a problem? Please describe. At the moment opensearch_dashboards.yml is stored as a ConfigMap. So the settings (incl. opensearch_security.openid.client_secret) are not really treated as 'Secrets'.

Describe the solution you'd like opensearch_dashboards.yml should be stored as a Secret instead of a ConfigMap.

Additional context In the opensearch chart files like config.yml etc. are already stored as Secrets instead of ConfigMaps.

[jordarlu]

@domruf , Could you elaborate more on converting the opensearch_dashboards.yml to a secret? if you can also contribute a PR for it? thanks !!

[domruf]

Okay, I'll look into creating my own pull request.