A gun violence prevention unit Attorney General Andrea Campbell announced Thursday will focus on enforcing the state’s gun and consumer protection laws while working to ensure Massachusetts has the “most comprehensive” gun laws on the books. Campbell appointed Christine Doktor, a former managing attorney at the gun safety group Everytown Law, to lead the unit and Ryan Mingo, former chief of the Major Felony Bureau at the Suffolk County District Attorney’s Office, to serve as second-in-command of