Paginate only after filtering in RssFeeds

[RafDevX]

RssFeeds (wrongly) starts by fetching 100 items from the database and only then filtering them, meaning that the final page size is inconsistent (depends on how many items "survive" the filter).

calypso/src/main/java/se/datasektionen/calypso/feeds/rss/RssFeeds.java

Line 61 in f9f39f8

.findAllPublished(PageRequest.of(0, 100, Sort.by(Sort.Direction.DESC, "publishDate")))

Instead, we should either filter in the database or find some other solution to ensure the page size is always 100 (if >=100 items exist).