LDAP search_key gotcha

[geoffgarside]

At $work we tend to use email addresses for AD/LDAP user authentication, so naturally when configuring LDAP authentication I used userPrincipalName instead of sAMAccountName as the search_key.

This ends up failing the authentication as Squash strips off the email suffix from the provided username. The setup.rb could potentially warn about this and swap userPrincipalName with sAMAccountName.