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

2 files changed, 13 insertions, 0 deletions

diff --git a/app/policies/application_policy.rb b/app/policies/application_policy.rb
index 3e617001f..d1de5e81a 100644
--- a/app/policies/application_policy.rb
+++ b/app/policies/application_policy.rb
@@ -15,4 +15,8 @@ class ApplicationPolicy
   def current_user
     current_account&.user
   end
+
+  def user_signed_in?
+    !current_user.nil?
+  end
 end
diff --git a/app/policies/backup_policy.rb b/app/policies/backup_policy.rb
new file mode 100644
index 000000000..0ef89a8d0
--- /dev/null
+++ b/app/policies/backup_policy.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class BackupPolicy < ApplicationPolicy
+  MIN_AGE = 1.week
+
+  def create?
+    user_signed_in? && current_user.backups.where('created_at >= ?', MIN_AGE.ago).count.zero?
+  end
+end