Allow setting OIDC providers other than Google, Azure, Okta

[chgl]

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

In https://github.com/acryldata/datahub-helm/blob/master/charts/datahub/subcharts/datahub-frontend/templates/deployment.yaml#L243 only google, okta, and azure are valid OIDC providers.
It would be great if arbitray providers can be specified as well.

Describe the solution you'd like

Allow setting an other provider with a custom discovery url.

Describe alternatives you've considered

Setting everything using extraEnv should work alternatively.

Additional context

I'd be happy to contribute this change!

[github-actions]

This issue is stale because it has been open for 30 days with no activity. If you believe this is still an issue on the latest DataHub release please leave a comment with the version that you tested it with. If this is a question/discussion please head to https://slack.datahubproject.io. For feature requests please use https://feature-requests.datahubproject.io