Email in Argo Server audit Log and GDPR

# Summary

Currently [argo server gatekeeper will log the email in an audit log](https://github.com/argoproj/argo-workflows/blob/d0cfc6d10b11d9977007bb14373e699e604c1b74/server/auth/gatekeeper.go#L314). This is not great because email is personally identifiable information in Europe and is subject to GDPR.

I suggest being able to choose what is logged/what is not logged through the argo server configmap. For example custom claims, groups etc.

# Use Cases

- In countries with GDPR or other personal information legislation explicitly disabling email logging
- More granular auditing. For example logging which OIDC group the user belongs to.

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**Message from the maintainers**:

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Start at server/auth/gatekeeper.go around line 314 and review how Argo Server audit logging and the ConfigMap relate. Clarify the configurable audit fields, including email, custom claims, and groups; done means users can select which identity data is logged, including disabling email logging.

Written by the indexing model from the issue text.