Fixes #9967 - make sure User.current is isolated

Refs #3809 - Remove cops for empty lines

Fixes #3840 - Removes unused Signo related code

fixes #6964 - replace default scope that hides users with explicit scope

fixes #3272 - allow 'admin' account to be removed and replaced

fixes #3892 - process REMOTE_USER_GROUP_N and REMOTE_USER_GROUP_#, add user to groups based on external user groups.

fixes #3528 - Populate first name, last name, and email, if available.

Fixes #3753 - always use main_app to determine paths for running an isolated namespace plugin

fixes #3312 - support /users/extlogin as a login page based on REMOTE_USER

fixes #3597 - removing rr gem, make tests consistent by using just mocha

Fixes #3043 - Support Signo on API level using BasicAuth

fixes #2988 - merge authentication code, enables REMOTE_USER auth on new API controllers

Fixes #2722 - Support for crossdomain auth

Newest Signo support authentication across more domains. We just need to
look not only to a cookie but parse parameters for getting username.

Fixes #2502 - session expiration updates

Signo now allows to transparently prolong user session which got
expired. Also when you now logout from Foreman you will end up in Signo
login form. This brings some code clean up and test changes and small
SSO method API change.

fixes #2417 - SSO abstractioning

Apache and Signo SSO reworked to a new general SSO concept.

You can use SSO service that comes with Katello for loggin in. It's
based on OpenID protocol with slightly customized provider.