BOSTON — The city of Boston has agreed to pay more than $2.1 million to the Christian legal organization that backed a court challenge after the city refused to fly a Christian flag outside City Hall, a case that made it all the way to the U.S. Supreme Court.The settlement announced Tuesday by Liberty Counsel covers attorneys’ fees and other costs associated with the legal battle that started in 2017 when city resident Hal Shurtleff and his Camp Constitution group asked to hoist the flag on one of three poles …