Authentication flow configuration

Authentication flow definitions are a new concept in Unity.

Authenticaton Flow config consists of:

• Set of 1st factor authenticators
• List of 2nd factor authenticators
• 2nd factor policy:
  • require
  • userOptIn (the default)
  • never
  • riskBased (in future, do not add it now)

This task is to define configuration of authentication flow as a separate entity in the system, its loading and exposing internally as objects.

Providing any sort of UI is out of scope.

Configuration format: properties. Loading at startup. Defined in unityServer.conf and all handling patterns similar as for authenticators.