Unit tests working again!
:lipstick:
:zap: Large refactor of the AuthenticationProviderFactory.
- Added a new interface: IAuthenticationProviderFactory.
- Added an IProviderScanner constructor dependency to the AuthenticationProviderFactory.
- The factory doesn't  need to do any of the 'smarts' to determine the providers anymore. This is now handled in the ProviderScanner class. This now means, that class can be injected AND can be a singleton.