Mark similar series: add integration tests

[0pdd]

The puzzle 1280-233d287d from #1280 has to be resolved:

mystamps/src/main/webapp/WEB-INF/views/series/info.html

Line 868 in 1391152

<!--/* @todo #1280 Mark similar series: add integration tests */-->

The puzzle was created by Slava Semushin on 12-Apr-20.

[php-coder]

We should also cover the case when multiple values were specified or it's a range of ids (see #1448)