Sender display name overwritten in user mails

When generating a mail the attribute mailer.Mail.From.Name gets initialized by claims.DisplayName (the requesting users display name). This value short after gets overwritten by the users login name (claims.Name) causing the login name to be used when writing the From mail header.

claims.Name should only be used if no display name is set for the user.

I prepared a short patch that fixes this (dev HEAD).

Fix included in PR (#58)