Different MD5 Username and the name used in AOR

I have a bunch of SIP clients which iam registering with the Asterisk server (Inside our LAN).Here is an excerpt from the sip.conf file


Now i have a option in my SIP client to configure a different MD5 username,but i could not find an option to configure the md5 username in the asterisk.I can successfully register with asterisk if i use 55591 as MD5 username otherwise iam not able to.So Is there an option to configure in asterisk to use different md5 username.Iam using Asterisk version (rc2) in Kubuntu.

After a lot of search in the issue tracker i found this statement by oej

Yes, Asterisk has a local policy that the user name part of the URI has to be the same as the digest auth user name. If we can’t find the user, there’s no point in authenticating. Also remember that most parts of the auth process is not in RFC3261, but in the RFCs that describe HTTP digest Auth.

in bug 0004982

Does this restriction still applies to the latest asterisk???