Use QSharedPointer instead of cloning YkChallengeResponseKey and make it a QObject to allow emitting signals

src/keys/YkChallengeResponseKey.h

@@ -22,20 +22,34 @@
 #include "keys/ChallengeResponseKey.h"
 #include "keys/drivers/YubiKey.h"
 
-class YkChallengeResponseKey : public ChallengeResponseKey
+#include <QObject>
+
+class YkChallengeResponseKey : public QObject, public ChallengeResponseKey
 {
+    Q_OBJECT
+
 public:
 
-    YkChallengeResponseKey(int slot = -1,
-                           bool blocking = false);
+    YkChallengeResponseKey(int slot = -1, bool blocking = false);
 
     QByteArray rawKey() const;
-    YkChallengeResponseKey* clone() const;
     bool challenge(const QByteArray& chal);
-    bool challenge(const QByteArray& chal, int retries);
+    bool challenge(const QByteArray& chal, unsigned retries);
     QString getName() const;
     bool isBlocking() const;
 
+signals:
+    /**
+     * Emitted whenever user interaction is required to proceed with the challenge-response protocol.
+     * You can use this to show a helpful dialog informing the user that his assistance is required.
+     */
+    void userInteractionRequired();
+
+    /**
+     * Emitted when the user has provided their required input.
+     */
+    void userConfirmed();
+
 private:
     QByteArray m_key;
     int m_slot;