[AFV] Signal/handling for authentication failures

* authentication issues in AFV were silently handled
* and there was no re-try, which could mean an initial glitch COULD cause AFV not working properly
* NOW handling in AFV client and context
* also reset connection data so for a new session no old authentication token or check time is used
* check for "invalid" QDateTime(s)

src/swiftguistandard/swiftguistd.cpp

@@ -444,6 +444,14 @@ void SwiftGuiStd::onRequestedConsoleMessage(const QString &logMsg, bool clear)
     log->appendPlainTextToConsole(logMsg);
 }
 
+void SwiftGuiStd::onAudioClientFailure(const CStatusMessage &msg)
+{
+    if (msg.isEmpty()) { return; }
+    if (!sGui || sGui->isShuttingDown()) { return; }
+
+    ui->fr_CentralFrameInside->showOverlayHTMLMessage(msg);
+}
+
 void SwiftGuiStd::focusInMainEntryField()
 {
     ui->comp_MainKeypadArea->focusInEntryField();