When Declan Lawn and Adam Patterson were first approached about making a cop show set in Belfast, they were — to put it mildly — apprehensive. Both writers grew up in Northern Ireland, live in Belfast and are deeply familiar with the bloody history of the region. Yet they worried that a series about the city’s police force, which was once overwhelmingly Protestant and viewed with suspicion by the Catholic community, would be too inherently polarizing. Even today, more than 25 years after the Good Friday Agreement, which brought peace to the country after decades of conflict, “There are some ar…