feat: SSO MFA - Add Auth Connector MFA settings protobuf and methods.

[Joerger]

Part of the implementation of SSO MFA

[github-actions]

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[Joerger]

@fspmarshall friendly reminder for review

[fspmarshall]

At a glance it looks like at least one of the new fields is a secret. I don't know much about oidc/saml so I'm not sure which other fields may also be sensitive, but the OIDCConnector and SAMLConnector resources both implement the ResourceWithSecrets interface and implement separate RBAC controls for reading the resources with and without secrets included. In practice, what this means is that any time you add a field either of these resources, their respective WithoutSecrets method must be updated to censor/omit the field if it is secret/sensitive.

LGTM once a pass has been done on WithoutSecrets.