create .odt with headings and table

I need to create a .odt file that contains headings (such as heading 1 or heading 2) and tables.

I tried something like this:

Code:

#include <QString>
#include <QTextStream>
#include <QTextDocument>
#include <QTextDocumentWriter>
 
int main(void)
{
    QString strStream;
    QTextStream out(&strStream);
 
    QTextDocument *document = new QTextDocument();
 
    out << "<!DOCTYPE html>"
        << "<html>\n"
        << "<head>"
        << "<title>Test</title>"
        << "</head>"
        << "<body>"
        << "<h1>Test heading 1</h1>"
        << "</body>"
        << "</html>";
    document->setHtml(strStream);
 
    QTextDocumentWriter writer("test.odt");
 
    writer.setFormat("odf");
    writer.write(document);
 
    delete document;
    return 0;
}

but the product .odt file has no heading.
Attachment 12910
what I would like to be heading 1 doesn't have the Heading 1 style, but, in fact, it's a Default Style bold text.

How do I force Heading 1 style?

best regards
Max