The exports page showed a different "CSV" capitalisation in the
"Bookmarks" row ("Csv") compared to the other rows ("CSV").
This was due to a referece to a translation string that does not exist,
`bookmarks.csv`, defaulting to the key's last segment in title case.

This issue was introduced in commit dcd86204 (PR #14956).

(h/t @meqif for helping with figuring out the bug)

* Add ability to export bookmarks

* Add support for importing bookmarks

* Add bookmark import tests

* Add bookmarks export test

Currently the page re-uses strings from other contexts which doesn't fit
very well - strings incorrectly lowercase-d and pluralized, when they
don't need to be, because it's a table.

This commit changes page to re-use accounts.posts_tab_heading for toots,
and admin.accounts for "Following" and "Follows". This all should look
more aesthetically pleasing.

Fix #10736

- Change data export to be available for non-functional accounts
- Change non-functional accounts to include redirecting accounts

Fix #6893
Fix #9268

* Group reports by target account

* Improve CSS

* Show exact number of followers/statuses on export page/in tooltip

* Fix tests

* Fix #201: Account archive download

* Export actor and private key in the archive

* Optimize BackupService

- Add conversation to cached associations of status, because
  somehow it was forgotten and is source of N+1 queries
- Explicitly call GC between batches of records being fetched
  (Model class allocations are the worst offender)
- Stream media files into the tar in 1MB chunks
  (Do not allocate media file (up to 8MB) as string into memory)
- Use #bytesize instead of #size to calculate file size for JSON
  (Fix FileOverflow error)
- Segment media into subfolders by status ID because apparently
  GIF-to-MP4 media are all named "media.mp4" for some reason

* Keep uniquely generated filename in Paperclip::GifTranscoder

* Ensure dumped files do not overwrite each other by maintaing directory partitions

* Give tar archives a good name

* Add scheduler to remove week-old backups

* Fix code style issue

* Scrollable tables in settings pages

* Add space before curly brace

* Refactor Export to take an account and know about the export types

* Use Export instance in settings/exports#show

* Allow export of mutes list

* Allow importing of mutes list

* Refactor to use Settings::Exports::BaseController and DRY up exports code

* Add basic coverage for settings/exports controller

* Remove unused @account variable from settings/exports controller

* Add coverage for download export actions

* Remove deprecated `render :text` in favor of `send_data` for csv downloads

* Add model to handle exports

* Use Export class in settings/exports controller

* Simplify settings/exports controller methods

* Move settings/export to more restful routes

Add ability to search accounts by display name