effects/screenshot: Add API version property to org.kde.ScreenShot2 interface

src/effects/screenshot/org.kde.KWin.ScreenShot2.xml

@@ -14,6 +14,13 @@
         a screen, or a window.
     -->
     <interface name="org.kde.KWin.ScreenShot2">
+        <!--
+            Version:
+
+            API version.
+        -->
+        <property name="Version" type="u" access="read"/>
+
         <!--
             CaptureWindow:
             @handle: The unique handle that identified the window

src/effects/screenshot/screenshotdbusinterface2.cpp

@@ -273,6 +273,11 @@ ScreenShotDBusInterface2::~ScreenShotDBusInterface2()
     QDBusConnection::sessionBus().unregisterObject(s_dbusObjectPath);
 }
 
+int ScreenShotDBusInterface2::version() const
+{
+    return 2;
+}
+
 bool ScreenShotDBusInterface2::checkPermissions() const
 {
     if (!calledFromDBus()) {

src/effects/screenshot/screenshotdbusinterface2.h

@@ -31,11 +31,14 @@ class ScreenShotSource2;
 class ScreenShotDBusInterface2 : public QObject, public QDBusContext
 {
     Q_OBJECT
+    Q_PROPERTY(int Version READ version CONSTANT)
 
 public:
     explicit ScreenShotDBusInterface2(ScreenShotEffect *effect);
     ~ScreenShotDBusInterface2() override;
 
+    int version() const;
+
 public Q_SLOTS:
     QVariantMap CaptureWindow(const QString &handle, const QVariantMap &options,
                               QDBusUnixFileDescriptor pipe);