Extra configurations to server config map

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

Our deployment need some initialization after starting server (such as enable auth backend/import team roles/OIDC/policies...). So it would be handle for us to be able to adding some configuration file into server deployment

**Describe the solution you'd like**
adding something like below into bottom of server config map spec
```
{{- if .Values.configuration.data }}
{{ toYaml .Values.configuration.data | indent 2 }}
{{- end }}
```

Start by locating the server config map template in the Helm chart and inspect how chart values are defined. Render the chart with configuration.data set, then verify that its contents appear in the server config map as requested; the issue's YAML snippet describes the expected result.

Written by the indexing model from the issue text.