Hong Kong CNN  —  They arrived in huge numbers on shared bikes after pedaling 30 miles in the evening chill, pumped by the adrenaline of youth and the thrill of embarking on a spontaneous adventure with friends. Nighttime bike rides to Kaifeng, an ancient city in central China’s Henan province known for its historic sites and soup dumplings, have been all the rage among college students in the nearby provincial capital Zhengzhou – a trend initially encouraged by the government as it sought to