Make sub-domains case-insensitive
    
    Currently the only type of supported sub-domains are AD domains which
    are not case-sensitive. To make it easier for Windows user we make
    sub-domains case-insensitive as well which allows to write the username
    in any case at the login prompt.
    
    If support for other types of sub-domains is added it might be necessary
    to set the case-sensitive flag based on the domain type.