Refactor Member#add_user for GitLab EE
Refactor Member#add_user for GitLab EE

GitLab EE extends Member#add_user by adding some LDAP specific flags.
Prior to these changes, the only way this could be done was by modifying
Member#add_user in place. This could lead to merge conflicts whenever a
developer wants to change this method.

To resolve this issue, the logic that EE extends has been moved into a
separate method with the appropriate arguments. This allows EE to extend
the logic by prepending the method using an EE specific module.

mmkassem/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git,iiet/iiet-git,mmkassem/gitlabhq,dreampet/gitlab,axilleas/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,dreampet/gitlab