Qt D-Bus: Document that users should not mix Q_PROPERTY and Q_SLOTS

Below is valid Qt C++ code. However, trying to expose this to D-Bus using qdbuscpp2xml/qdbusxml2cpp might cause problems (see QTBUG-115629 ): setValue() might be exposed twice: Once as a D-Bus Property setter, and once as a D-Bus Method.

Code
Adapted from the example at https://doc.qt.io/qt-6/signalsandslots.html

// counter.h
#ifndef COUNTER_H
#define COUNTER_H
#include <QObject>

class Counter : public QObject
{
    Q_OBJECT
    Q_PROPERTY(int value READ value WRITE setValue NOTIFY valueChanged);

public:
    Counter(QObject* parent = nullptr) : QObject(parent) {}
    int value() const { return m_value; }

public slots:
    void setValue(int value);

signals:
    void valueChanged(int newValue);

private:
    int m_value = 0;
};
#endif

Suggestion
Document that users should either:

• Avoid marking Q_PROPERTY setters as slots, OR
• Use the `-m` option on qdbuscpp2xml to avoid exposing setValue() as a standalone Method