The Vatican announced Wednesday that Pope Francis had given his approval to the decision to canonize the Rev. Junipero Serra, an 18th-century missionary who brought Christianity to the American Indians along the West Coast. Some Native Americans have questioned Father Serra’s saintly nature, saying that Father Serra, a Franciscan missionary, imposed Christianity even as he suppressed local culture and traditions. Others have accused Father Serra of mistreating Indians. The pope said in January that he would celebrate Father Serra’s canonization Mass in Washington during his trip to the United States in September.