Minor fixes when reporting T141

* user authenticated must be enabled/valid
* Read only: BlackMisc::CDataReadOnly<BlackCore::Data::TAuthenticatedDbUser>
* clear user fields when not authenticated

src/blackcore/db/databaseauthentication.cpp

@@ -172,7 +172,7 @@ namespace BlackCore
 
         void CDatabaseAuthenticationService::userChanged()
         {
-            // code goes here
+            // this->logoff();
         }
     } // ns
 } // ns