The sun sparkles over San Sebastián’s bay and harbour, not far from the old town with its winding streets, historic churches and regal square. The serene landscape and traditional Spanish snacks are all part of its appeal to tourists – and the tour operators who fuel the influx of guests. But residents here and in an increasing number of Spanish cities are growing annoyed by the crowds, noise and housing shortages associated with mass tourism. The transformation of apartments into tourist quarters is also controversial, reducing the living space available to locals and driving up prices. Curre…