LANCASTER, Pa. — Gerald Groff liked his work as a postal employee in Pennsylvania’s Amish Country. For years, he delivered mail and all manner of packages: a car bumper, a mini refrigerator, a 70-pound box of horseshoes for a blacksmith. But when an Amazon.com contract with the Postal Service required carriers to start delivering packages on Sundays, Groff balked. A Christian, he told his employers that he couldn’t deliver packages on the Lord’s Day.Now Groff’s dispute with the Post Office has …