Add debug messages on tariff config initialisation

library/src/calculate_price.cpp

@@ -49,14 +49,27 @@ bool CALCULATE_LIBRARY_API init_tariff(parking_tariff_t **tariff, char const *co
     snprintf(buffer, sizeof(buffer)-1, "tariff%02d.json", zone);
     confFile += buffer;
 
+    // DEBUG
+    qCritical() << "      ... confFile = " << confFile;
+
     QFile fname(confFile);
     if (fname.exists()) {
+
+        // DEBUG
+        qCritical() << "      ... confFile exists";
+
         if (fname.open(QIODevice::ReadOnly | QIODevice::Text)) {
+
+            // DEBUG
+            qCritical() << "      ... confFile is open";
+
             QString json = fname.readAll();
             return (*tariff)->ParseJson(*tariff, json.toStdString().c_str());
         }
     }
 
+    qCritical() << "init_tariff: Parsing tariff config (" << confFile << ") failed!";
+
     return false;
 }