DirectMappedPersonAttributeDao is netId case-sensitive

[robertoschwald]

When authenticating the user, it might be possible that the attributes are not found in the attributeMap of DirectMappedPersonAttributeDao when the username contains mixed-case letters, as the netId is used as the key to the map entry.

Workarounds

1. convert the username to lowercase in UsernamePasswordCredentials

Possible fix:
Change the DirectMappedPersonAttributeDao to always use the netId map key as lowercase.