Maybe it’s the gluten-free appeal, but suddenly cider is everywhere. Programs are deepening, from downtown, where poutine purveyor Saus just expanded its selection, to Heritage of Sherborn, the new venture from Brookline’s La Morra team, which offers two taps and cider flights in the suburb that was once home to the world’s largest refined cider mill. And dedicated taprooms have popped up in Charlestown, home to Downeast Cider House, in Somerville, home to Bantam Cider Company, and in Natick, where the centuries-old Belkin Family Lookout Farm recently added a charcuterie-augmented taproom that’ll lure even the certifiably citified.