Move all environment variables to a ConfigMap

[jgwerner]

Create a ConfigMap to manage all environment variables. This will help centralize environment variables that are currently located in the custom JupyterHub configuration as well as in various other locations.

For example:

apiVersion: v1
kind: ConfigMap
metadata:
  name: illumidesk-keycloak
  namespace: {{ .Release.Namespace }}
  labels: {{- include "common.labels.standard" . | nindent 4 }}
    app.kubernetes.io/component: keycloak
    {{- if .Values.commonLabels }}
    {{- include "common.tplvalues.render" ( dict "value" .Values.commonLabels "context" $ ) | nindent 4 }}
    {{- end }}
  {{- if .Values.commonAnnotations }}
  annotations: {{- include "common.tplvalues.render" ( dict "value" .Values.commonAnnotations "context" $ ) | nindent 4 }}
  {{- end }}
data:
  KEYCLOAK_CREATE_ADMIN_USER: {{ ternary "true" "false" .Values.auth.createAdminUser | quote }}
  KEYCLOAK_ADMIN_USER: {{ .Values.auth.adminUser | quote }}
  POSTGRES_USER:  {{ .Values.auth.postgresUser | quote }}
  ...

[jgwerner]

@Abhi94N based on our comments, mount the config map and secrets to the hub's sub-chart to also add extraMounts to the grader-setup-service. The shared grader notebooks could have these mounts as well (set by the grader-setup-service) to access these values.