[RFE] Support Keystone as an OIDC auth provider

[Fryguy]

Some information - https://docs.openstack.org/keystone/latest/admin/federation/configure_federation.html

[miq-bot]

This issue has been automatically marked as stale because it has not been updated for at least 3 months.

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[miq-bot]

This issue has been automatically closed because it has not been updated for at least 3 months.

Feel free to reopen this issue if this issue is still valid.

Thank you for all your contributions! More information about the ManageIQ triage process can be found in the triage process documentation.