What was the legend of the "áureo racimo" (golden cluster) in Hungary?

A legend was created about the existence of a golden vine in Hungary, which produced golden tendrils and leaves.
The legend was fueled by the discovery of golden tendrils in Hungarian vineyards.
The legend also included the existence of golden grapes, which were said to contain actual grains of gold.
The legend was based on the discovery of ancient Celtic jewelry, which had been buried and later uncovered by vine roots.