chatgui: invite link dialogs, zxing-cpp QR code, crypto transport, channel improvements; msg_transport: chat protocol support

tools/chatgui/src/qrcode_utils.cpp

@@ -0,0 +1,26 @@
+#include "qrcode_utils.h"
+#include "ZXingQt.h"
+
+QImage generateQRCode(const QString& text, int moduleSize)
+{
+    using namespace ZXingQt;
+    auto barcode = Barcode::fromText(text, BarcodeFormat::QRCode);
+    if (!barcode.isValid())
+        return {};
+    WriterOptions opts;
+    if (moduleSize > 0)
+        opts.scale(moduleSize);
+    return barcode.toImage(opts);
+}
+
+QStringList readQRCodes(const QImage& image)
+{
+    using namespace ZXingQt;
+    auto results = ReadBarcodes(image);
+    QStringList texts;
+    for (const auto& b : results) {
+        if (b.isValid())
+            texts.append(b.text());
+    }
+    return texts;
+}