SeriesService.countStampsOf(): rename to CollectionService.countStampsOf()

[0pdd]

The puzzle 477-49c1b317 from #477 has to be resolved:

mystamps/src/main/java/ru/mystamps/web/service/SeriesService.java

Line 39 in 4cb3692

// @todo #477 SeriesService.countStampsOf(): rename to CollectionService.countStampsOf()

The puzzle was created by Slava Semushin on 13-Jun-18.