* LDAP: use only one struct
* Use only models.ExternalUserInfo
* Add additional helper method :/
* Move all the helpers to one module
* LDAP: refactoring
* Rename some of the public methods and change their behaviour
* Remove outdated methods
* Simplify logic
* More tests
There is no and never were tests for settings.go, added tests for helper
methods (cover is now about 100% for them). Added tests for the main
LDAP logic, but there is some stuff to add. Dial() is not tested and not
decoupled. It might be a challenge to do it properly
* Restructure tests:
* they wouldn't depend on external modules
* more consistent naming
* logical division
* More guards for erroneous paths
* Login: make login service an explicit dependency
* LDAP: remove no longer needed test helper fns
* LDAP: remove useless import
* LDAP: Use new interface in multildap module
* LDAP: corrections for the groups of multiple users
* In case there is several users their groups weren't detected correctly
* Simplify helpers module
