oidc: support multiple OIDC identifiers for a single identity

[noells]

Related issue(s)

Checklist

• [ ] I have read the contributing guidelines.
• [ ] I have referenced an issue containing the design document if my change introduces a new feature.
• [ ] I am following the contributing code guidelines.
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• [ ] I have added tests that prove my fix is effective or that my feature works.
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Further Comments

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