Support `logLevel` helm value in `extauth`

[pmichna]

To configure log level for extauth via Helm values I need to use:

global:
  extensions:
    extAuth:
      deployment:
        customEnv:
          - name: LOG_LEVEL
            value: warn

Other components support logLevel value (e.g. gloo.gloo.logLevel). It would be nice to have the same approach in extauth.

[chrisgaun]

@sam-heilbron can you add information and links to docs

[sam-heilbron]

@pmichna We have a feature in the helm chart that allows further customization: https://docs.solo.io/gloo-edge/latest/reference/helm_chart_values/open_source_helm_chart_values/#helm-chart-kuberesourceoverrides.

[pmichna]

@sam-heilbron I know but it's as bad as global.extensions.extAuth.deployment.customEnv. :) It's even more complicated when extauth is in sidecar mode.