Move PIN generation into ComputerManager to be shared with CLI pairing

app/backend/computermanager.cpp

@@ -10,6 +10,8 @@
 #include <QThreadPool>
 #include <QCoreApplication>
 
+#include <random>
+
 #define SER_HOSTS "hosts"
 
 class PcMonitorThread : public QThread
@@ -826,4 +828,14 @@ void ComputerManager::addNewHost(NvAddress address, bool mdns, NvAddress mdnsIpv
     QThreadPool::globalInstance()->start(addTask);
 }
 
+// TODO: Use QRandomGenerator when we drop Qt 5.9 support
+QString ComputerManager::generatePinString()
+{
+    std::uniform_int_distribution<int> dist(0, 9999);
+    std::random_device rd;
+    std::mt19937 engine(rd());
+
+    return QString::asprintf("%04u", dist(engine));
+}
+
 #include "computermanager.moc"