New attachment mechanism. Also add image from clipboard.

src/imageclipboard.h

@@ -0,0 +1,29 @@
+#ifndef IMAGECLIPBOARD_H
+#define IMAGECLIPBOARD_H
+
+#include <QClipboard>
+#include <QImage>
+#include <QObject>
+
+class ImageClipboard : public QObject {
+  Q_OBJECT
+  Q_PROPERTY(bool hasImage READ hasImage NOTIFY imageChanged)
+  Q_PROPERTY(QImage image READ image NOTIFY imageChanged)
+
+ public:
+  explicit ImageClipboard(QObject* parent = nullptr);
+
+  bool hasImage();
+  QImage image();
+
+ private:
+  QClipboard* m_clipboard;
+
+ signals:
+  void imageChanged();
+
+ public slots:
+  void saveImage(const QUrl& localPath);
+};
+
+#endif  // IMAGECLIPBOARD_H