feat(app/App): better translations support

tests/src/app/App.cpp

@@ -27,20 +27,21 @@
 App *App::m_instance = nullptr;
 
 App::App (int &argc, char **argv) : QApplication(argc, argv) {
-  QString current_locale = QLocale::system().name();
-
-  if (m_english_translator.load(LANGUAGES_PATH "en"))
+  if (m_english_translator.load(QLocale(QLocale::English), LANGUAGES_PATH))
     installTranslator(&m_english_translator);
   else
     qWarning("Unable to install english translator.");
 
   // Try to use default locale.
-  if (m_default_translator.load(QString(LANGUAGES_PATH) + current_locale)) {
+  QLocale current_locale = QLocale::system();
+
+  if (m_default_translator.load(current_locale, LANGUAGES_PATH)) {
     installTranslator(&m_default_translator);
-    m_locale = current_locale;
-  } else
+    m_locale = current_locale.name();
+  } else {
     qWarning() << QStringLiteral("Unable to found translations for locale: %1.")
-      .arg(current_locale);
+      .arg(current_locale.name());
+  }
 
   setWindowIcon(QIcon(WINDOW_ICON_PATH));