Add pagination to archives
As suggested by @viktomas, https://gitlab.com/gitlab-org/gitter/webapp/-/merge_requests/1887#note_354136293
Add pagination to archives to split a busy day into multiple chunks.
In https://gitlab.com/gitlab-org/gitter/webapp/-/merge_requests/1887, we limited archive pages to only showing 1,500 messages for a given day. This means that rooms with lots of activity have missing messages from that day when they visit the archive.
We started limiting the archive to 1,500 messages because it causes spikes in MongoDB and the page isn't even responsive with that many messages anyway.
"Complete history archives(indexed by search engines)" is one of our main differentiating factors so it would be good to get everything available again.