Allow appending of domain name to username for logins

[fabiang]

Hello,

my company started to deprecate sAMAccountName in our Active Directory and try to switch all application over to use userPrincipalName. Unfortunately userPrincipalName contains the domain name suffix.

To make it more comfy for our users not require to write "username@domain", I've added a setting to always append the domain name automatically to the username.

See here:

I've provided translations for English and German. Also the settings field ad_domain is now required when is_ad is checked.

Thanks!

[snipe]

Funny, we were just talking about adding this - nice work, thanks!