QAbstractHttpServer not supporting certificate chains

Hi!

I am using QHttpServer for a Viber bot and yesterday stopped working because they changed something and from now on if you have a Let's Encrypt certificate for free than you have a chain in it and that is not working together with the new Viber setup. The current implementation in the QHttpServer the 

 void sslSetup(const QSslCertificate &certificate, ... ); 

function only supports one certificate to send to the Viber framework which leads to a TLS error "Alert (Level: Fatal, Description: Certificate unknown)" and the socket is closed. This happend only when you tried to send a message from a Phone/PC client to the bot. When the bot communicated with the Viber framework it worked fine.

I am proposing this simple fix to solve this problem:
Add to class QAbstractHttpServer in qabstracthttpserver.h : 48. :

#if QT_CONFIG(ssl)
    void sslSetup(const QSslCertificate &certificate, const QSslKey &privateKey,
                  QSsl::SslProtocol protocol = QSsl::SecureProtocols);
    void sslSetup(const QList<QSslCertificate> &certificates, const QSslKey &privateKey,
                  QSsl::SslProtocol protocol = QSsl::SecureProtocols);
    void sslSetup(const QSslConfiguration &sslConfiguration);
#endif

add to the qabstracthttpserver.cpp : 260

void QAbstractHttpServer::sslSetup(const QList<QSslCertificate> &certificates,
                                   const QSslKey &privateKey, QSsl::SslProtocol protocol)
{
    QSslConfiguration conf;
    conf.setLocalCertificateChain(certificates);
    conf.setPrivateKey(privateKey);
    conf.setProtocol(protocol);
    sslSetup(conf);
}

With this small change the Viber bot started to work again.

Thank you!