Add some boring documentation for data control wrappers

This change adds some documentation that describes the purpose of data
control wrappers in a few words.

src/wayland/datacontroldevice_v1_interface.h

@@ -17,21 +17,17 @@ namespace KWaylandServer
 
 class AbstractDataSource;
 class DataControlDeviceManagerV1Interface;
+class DataControlDeviceV1InterfacePrivate;
 class DataControlOfferV1Interface;
 class DataControlSourceV1Interface;
 class SeatInterface;
 class SurfaceInterface;
 
 /**
- * @brief Represents the Resource for the wl_data_device interface.
+ * The DataControlDeviceV1Interface extensions allows clients to manage seat's current selection.
  *
- * @see SeatInterface
- * @see DataControlSourceV1Interface
- * Lifespan is mapped to the underlying object
- **/
-
-class DataControlDeviceV1InterfacePrivate;
-
+ * DataControlDeviceV1Interface corresponds to the Wayland interface @c zwlr_data_control_device_v1.
+ */
 class KWAYLANDSERVER_EXPORT DataControlDeviceV1Interface : public QObject
 {
     Q_OBJECT

src/wayland/datacontroldevicemanager_v1_interface.h

@@ -19,9 +19,11 @@ class DataControlDeviceManagerV1InterfacePrivate;
 class DataControlDeviceV1Interface;
 
 /**
- * @brief Represents the Global for zwlr_data_control_manager_v1 interface.
+ * The DataControlDeviceManagerV1Interface provides a way for privileged clients such as clipboard
+ * managers to manage the current selection.
  *
- **/
+ * DataControlDeviceManagerV1Interface corresponds to the Wayland interface @c zwlr_data_control_manager_v1.
+ */
 class KWAYLANDSERVER_EXPORT DataControlDeviceManagerV1Interface : public QObject
 {
     Q_OBJECT

src/wayland/datacontroloffer_v1_interface.h

@@ -23,9 +23,10 @@ class DataControlSourceV1Interface;
 class DataControlOfferV1InterfacePrivate;
 
 /**
- * @brief Represents the Resource for the wl_data_offer interface.
- * Lifespan is mapped to the underlying object
- **/
+ * The DataControlOfferV1Interface extension represents a piece of data offered for transfer.
+ *
+ * DataControlOfferV1Interface corresponds to the Wayland interface @c zwlr_data_control_offer_v1.
+ */
 class KWAYLANDSERVER_EXPORT DataControlOfferV1Interface : public QObject
 {
     Q_OBJECT

src/wayland/datacontrolsource_v1_interface.h

@@ -18,9 +18,10 @@ namespace KWaylandServer
 class DataControlSourceV1InterfacePrivate;
 
 /**
- * @brief Represents the Resource for the zwlr_data_control_source_v1 interface.
- * Lifespan is mapped to the underlying object
- **/
+ * The DataControlSourceV1Interface class represents the source side in a data transfer.
+ *
+ * DataControlSourceV1Interface corresponds to the wayland interface zwlr_data_control_source_v1.
+ */
 class KWAYLANDSERVER_EXPORT DataControlSourceV1Interface : public AbstractDataSource
 {
     Q_OBJECT