Account archive download (#6460)

* 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

1 files changed, 3 insertions, 0 deletions

diff --git a/spec/fabricators/backup_fabricator.rb b/spec/fabricators/backup_fabricator.rb
new file mode 100644
index 000000000..99a5bdcda
--- /dev/null
+++ b/spec/fabricators/backup_fabricator.rb
@@ -0,0 +1,3 @@
+Fabricator(:backup) do
+  user
+end