qt: use persisted profile, not off-the-record

When we upgraded from Qt 5.15 to Qt 6, the default profile seemed to
have changed from being stored on disk to off-the-record:

- https://doc.qt.io/qt-5/qwebengineprofile.html#defaultProfile
- https://doc.qt.io/qt-6.5/qwebengineprofile.html#defaultProfile

This made the third party widgets (MoonPay, Pocket, ...) lose their
cookies/localstorage upon app restart.

This commit switches our profile to be stored on disk once more. We
choose a new storage name "BitBoxApp" (not "Default" which was used
previously) to not run into potential conflicts or very old
user sessions that get unexpectedly resumed.

Author: benma

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Fix wrong estimated confirmation time for ERC20 tokens.
 - Enable unlock test wallet in testnet
 - Added support to show on the BitBox when a transaction's recipient is an address of a different account on the device.
+- Persist third party widget sessions
 
 # v4.47.2
 - Linux: fix compatiblity with some versions of Mesa that are incompatible with the bundled wayland libraries

frontends/qt/main.cpp

@@ -65,6 +65,7 @@
 // their CSP response headers.
 static const char* scheme = "bitboxapp";
 
+static QWebEngineProfile* profile;
 static QWebEngineView* view;
 static QWebEnginePage* mainPage;
 static QWebEnginePage* externalPage;
@@ -91,7 +92,7 @@ class BitBoxApp : public SingleApplication
 
 class WebEnginePage : public QWebEnginePage {
 public:
-    WebEnginePage(QObject* parent) : QWebEnginePage(parent) {}
+    WebEnginePage(QWebEngineProfile* profile) : QWebEnginePage(profile) {}
 
     QWebEnginePage* createWindow(QWebEnginePage::WebWindowType type) {
         Q_UNUSED(type);
@@ -353,7 +354,8 @@ int main(int argc, char *argv[])
     }
 
     externalPage = new QWebEnginePage(view);
-    mainPage = new WebEnginePage(view);
+    profile = new QWebEngineProfile("BitBoxApp");
+    mainPage = new WebEnginePage(profile);
     view->setPage(mainPage);
 
     pageLoaded = false;
@@ -459,6 +461,12 @@ int main(int argc, char *argv[])
         webClass = nullptr;
         delete view;
         view = nullptr;
+        // Make sure mainPage is deleted before the profile. This is a requirement for the profile
+        // to be able to flush to disk properly.
+        delete mainPage;
+        mainPage = nullptr;
+        delete profile;
+        profile = nullptr;
         webClassMutex.unlock();
         backendShutdown();
     });