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

config/locales/en.yml

@@ -421,6 +421,13 @@ en:
       title: This page is not correct
     noscript_html: To use the Mastodon web application, please enable JavaScript. Alternatively, try one of the <a href="https://github.com/tootsuite/documentation/blob/master/Using-Mastodon/Apps.md">native apps</a> for Mastodon for your platform.
   exports:
+    archive_takeout:
+      date: Date
+      download: Download your archive
+      hint_html: You can request an archive of your <strong>toots and uploaded media</strong>. The exported data will be in ActivityPub format, readable by any compliant software.
+      in_progress: Compiling your archive...
+      request: Request your archive
+      size: Size
     blocks: You block
     csv: CSV
     follows: You follow
@@ -733,6 +740,10 @@ en:
     setup: Set up
     wrong_code: The entered code was invalid! Are server time and device time correct?
   user_mailer:
+    backup_ready:
+      explanation: You requested a full backup of your Mastodon account. It's now ready for download!
+      subject: Your archive is ready for download
+      title: Archive takeout
     welcome:
       edit_profile_action: Setup profile
       edit_profile_step: You can customize your profile by uploading an avatar, header, changing your display name and more. If you’d like to review new followers before they’re allowed to follow you, you can lock your account.

config/routes.rb

@@ -76,7 +76,7 @@ Rails.application.routes.draw do
     resource :notifications, only: [:show, :update]
     resource :import, only: [:show, :create]
 
-    resource :export, only: [:show]
+    resource :export, only: [:show, :create]
     namespace :exports, constraints: { format: :csv } do
       resources :follows, only: :index, controller: :following_accounts
       resources :blocks, only: :index, controller: :blocked_accounts

config/sidekiq.yml

@@ -30,3 +30,6 @@
   email_scheduler:
     cron: '0 10 * * 2'
     class: Scheduler::EmailScheduler
+  backup_cleanup_scheduler:
+    cron: '<%= Random.rand(0..59) %> <%= Random.rand(3..5) %> * * *'
+    class: Scheduler::BackupCleanupScheduler