Afghanistan has long been known as a major producer of drugs - but now it's become one of the worst consumers of illegal drugs in the world. High unemployment, war trauma and easy access to refined heroin have resulted in more than a million Afghans being addicted to drugs. As part of 2013: The Big Stories, another chance to see BBC Persian's reporter Tahir Qadiry travel to Afghanistan to understand the extent of the problem. He follows a young addict as he makes his way…