code: public static AuthenticationData createAuthenticationData(String userName, UserRegistry userRegistry) {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) {
              SibTr.entry(tc, CLASS_NAME + "createAuthenticationData", userName);
          }
          AuthenticationData authData = new WSAuthenticationData();
          if (userName == null) {
              userName = "";
          }
          String realm = getDefaultRealm(userRegistry);
          authData.set(AuthenticationData.USERNAME, userName);
          authData.set(AuthenticationData.REALM, realm);
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled()) {
              SibTr.exit(tc, CLASS_NAME + "createAuthenticationData", authData);
          }
          return authData;
      }
docs: Create the AuthenticationData from the UserName
  
  @param userName
  @return