@Override
    public UserGroupInformation getUser() {
      if (username == null || "".equals(username)) {
        return null;
      }
      return UserGroupInformation.createRemoteUser(username);
    }
A custom token identifier for our custom auth'n method. Unique from the TokenIdentifier used
for delegation tokens.
hbase-server/src/test/java/org/apache/hadoop/hbase/security/provider/CustomSaslAuthenticationProviderTestBase.java