[OJS.de - OA-S II - ap 5: metrics API] implement report generator backend
[OJS.de - OA-S II - ap 6: default metric type] implement
[OJS.de - OA-S II - ap 5: metrics API] implement metrics API for OA-S plugin
[OJS.de - OA-S II - ap 7: most-read articles] scaffolding