Today was apparently “sign a service member” day in the NFL. Former Army safety Caleb Campbell has been offered a contract by the Detroit Lions, according to goblackknights.com. This news comes on the heels of former Air Force Academy all-purpose man Chad Hall inking a deal with the Philadelphia Eagles. Campbell is still stationed at Fort Sill, Okla., according to goblackknights.com, but is in the process of being released from active duty. Campbell was drafted by the Lions in the seventh round of the 2008 draft. He attended a team mini-camp but was denied the chance to sign a contract…