Add an option to fill participant input with default values using OIDC provider

[spiritedsnowcat]

As an end user, I'd like the participant dialog's name and email fields to contain my SSO name and email by default.

If an OpenID Connect provider for SSO has been configured as a separate identity source and where rallly has recorded name and email values from OIDC claims, it would be a nice-to-have feature if those values are used as defaults in the participant dialog window's fields.

Thanks for your time and for adding OIDC features. ✌️