Pagination may result in feedback conversations reappearing on other pages

[etanttila]

Due to how the pagination and the display of conversation history is implemented, if a student has responded multiple times to a given feedback exercise so that the responses would appear on different pages (e.g. sorting based on time (oldest first, newest first) and there has been time between responses so enough other responses lead to them being on different pages), the conversations would be displayed on both pages. This is due to changes made in PR #59, which I did not realize at the time, since I tested with so little data, that pagination did not happen. If the responses would be one the same page, the conversation appears just once (at the position of whichever would come first based on sorting)

The bug/feature could be mitigated by again adding the option to display only newest responses, (in which case the history is still displayed, of course, but the other search terms would be limited to searching only the newest messages when that filter is in use), but it wouldn't actually solve the issue fully. If one wants to really fix the base root of this, one would need to fix how the pagination and the FeedbackListView work together.