Add hint with what to do to warning

source/RobotAPI/libraries/armem/core/longtermmemory/Memory.cpp

@@ -15,7 +15,11 @@ namespace armarx::armem::ltm
         // Check connection:
         if (!MongoDBConnectionManager::ConnectionIsValid(dbsettings))
         {
-            ARMARX_WARNING << deactivateSpam("ConnectionIsNotValid") << "The connection to mongocxx for memory '" << name() << "' is not valid. Settings are: " << dbsettings.toString();
+            ARMARX_WARNING << deactivateSpam("ConnectionIsNotValid")
+                           << "The connection to mongocxx for memory '" << name() << "' is not valid. Settings are: " << dbsettings.toString()
+                           << "\nTo start it, run e.g.: \n"
+                           << "mongod --port " << dbsettings.port << " --dbpath \"/tmp/\""
+                           << "\n\n";
             return false;
         }
         ARMARX_INFO << "Checking connection";