templates: Support Nested YAML for GCFG Configuration

Enhancement: Support Nested YAML for GCFG Configuration

1. Problem Statement

Currently, our rstudio-library.config.gcfg template only supports a "flat" map structure. To generate configuration headers with subsections—such as [OTLPEndpoint "default"]—users are forced to use escaped string keys in their values.yaml:

    'OTLPEndpoint "default"':
      Endpoint: http://localhost:4318

or how we show here in our docs

This is error-prone, difficult to read, and breaks standard Helm nesting conventions, which makes deep-merging or using --set flags difficult.

2. Proposed Solution

Update the gcfg helper template to detect the data type of the section values.

• If the value is a Map, it should automatically render a nested header: [Section "Subsection"].
• If the value is a Simple Type (string/bool), it should continue to render the legacy flat header: [Section].

3. Implementation Plan

Introduce a "Hybrid" template logic using kindIs "map" to differentiate between the two input styles.

Proposed Template Logic:

    {{- define "rstudio-library.config.gcfg" -}}
    {{- range $section, $content := . -}}
      {{/* Determine if this section contains subsections or just key-values */}}
      {{- $isNested := false -}}
      {{- range $k, $v := $content -}}
        {{- if kindIs "map" $v -}}
          {{- $isNested = true -}}
        {{- end -}}
      {{- end -}}

      {{- if $isNested -}}
        {{/* New Way: Supports nested YAML maps */}}
        {{- range $sub, $vals := $content }}
    [{{ $section }} "{{ $sub }}"]
          {{- range $k, $v := $vals }}
    {{ $k }} = {{ $v }}
          {{- end }}
        {{- end }}
      {{- else -}}
        {{/* Legacy Way: Supports flat keys with manual quotes */}}
    [{{ $section }}]
        {{- range $k, $v := $content }}
    {{ $k }} = {{ $v }}
        {{- end }}
      {{- end }}
    {{- end -}}
    {{- end -}}

4. Backwards Compatibility

This change is non-breaking:

1. Existing configurations using 'Section "Sub"': will still enter the else block and render exactly as they do today.
2. New configurations can use the cleaner nested syntax, which is more "Helm-native."

5. Example Comparison

Locate the rstudio-library.config.gcfg helper and compare its current flat rendering with the nested values.yaml examples in the issue. Verify that both legacy quoted section keys and nested map input render the expected GCFG headers and key-value lines, including the documented OTLPEndpoint example.