Adding (now empty) Email auth manager
Populate the session with an ID to represent the email account
Changing the portions where session is populated with from system to use the enum of AuthenticationProviderTypes
Renaming classes, variables and methods to properly name things as "Authentication Provider" identities instead of "External" identities.  Main reason is that CRS itself is now an auth provider and external doesn't make sense anymore
Cleaning compile issues in tests due to previous refactoring
Update database schema... renaming table to better reflect what's stored inside.
Adding column to store email account access code
Verify auth id header value for incoming requests.
Additional refactoring of names and such for clarity (external -> auth_provider)
Renaming database table this identity references