fix: extraEnv requires only string values now

[olevski]

So I saw the helm lint failed after the latest changes. But the line that causes the failure has not been changed in months.

I think this is occurring because jupyterhub was upgraded.

This is the line in the jupyterhub helm chart _helpers.tpl that causes this problem:

{{- else if eq (typeOf $value) "string" -}}
- name: {{ $key | quote }}
  value: {{ $value | quote | println }}
{{- else }}
{{- printf "?.extraEnv.%s had an unexpected type (%s)" $key (typeOf $value) | fail }}
{{- end }}

It seems that before non-string values were allowed in the extraEnv part, but not anymore. The lint command passes after this.

[pameladelgado]

Good catch! 👍