Added secret service preprocessor for OIDC auth client

[winklerj]

What has changed?

• Secret service: Created an auth client preprocessor to map the id_token into the secret value
• Also, mapped the email in the JWT to the externalId like the Microsoft preprocessor

Does a specific change require especially careful review?

This functionality is modeled after other preprocessors that exist in the code and should be low risk

What is still open or a known issue?
N/A

Release Notes
Added secret service auth client preprocessor for mapping an Open ID Connect (OIDC) id_token into the secret value created from the auth client.

[RobinBrinkmann]

Thanks for your contribution @winklerj and review @sachmerz.
PR approved and merged.