Add traffic stats to mgmt API

Signed-off-by: Kai Zimmermann <kai.zimmermann@bosch-si.com>

hawkbit-mgmt-resource/src/main/java/org/eclipse/hawkbit/mgmt/rest/resource/MgmtSystemManagementResource.java

@@ -87,6 +87,7 @@ public class MgmtSystemManagementResource implements MgmtSystemManagementRestApi
         result.setArtifacts(tenant.getArtifacts());
         result.setOverallArtifactVolumeInBytes(tenant.getOverallArtifactVolumeInBytes());
         result.setTargets(tenant.getTargets());
+        result.setOverallArtifactTrafficInBytes(tenant.getOverallArtifactTrafficInBytes());
 
         return result;
     }