Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- `README.md`:
  Our README.md files are completely different. Discarded upstream changes.
- `app/javascript/core/admin.js`:
  Updating rails-ujs, no real conflict, but a comment to close to changed
  code. Various glitch-soc-only files have been updated to match those changes,
  though.
- `package.json`:
  No real conflict, just an additional dependency in glitch-soc that was too
  close to something updated upstream. Took upstream's changes.

app/workers/backup_worker.rb

@@ -9,8 +9,12 @@ class BackupWorker
     backup_id = msg['args'].first
 
     ActiveRecord::Base.connection_pool.with_connection do
-      backup = Backup.find(backup_id)
-      backup&.destroy
+      begin
+        backup = Backup.find(backup_id)
+        backup.destroy
+      rescue ActiveRecord::RecordNotFound
+        true
+      end
     end
   end
 

app/workers/post_process_media_worker.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+class PostProcessMediaWorker
+  include Sidekiq::Worker
+
+  sidekiq_options retry: 1, dead: false
+
+  sidekiq_retries_exhausted do |msg|
+    media_attachment_id = msg['args'].first
+
+    ActiveRecord::Base.connection_pool.with_connection do
+      begin
+        media_attachment = MediaAttachment.find(media_attachment_id)
+        media_attachment.processing = :failed
+        media_attachment.save
+      rescue ActiveRecord::RecordNotFound
+        true
+      end
+    end
+
+    Sidekiq.logger.error("Processing media attachment #{media_attachment_id} failed with #{msg['error_message']}")
+  end
+
+  def perform(media_attachment_id)
+    media_attachment = MediaAttachment.find(media_attachment_id)
+    media_attachment.processing = :in_progress
+    media_attachment.save
+    media_attachment.file.reprocess_original!
+    media_attachment.processing = :complete
+    media_attachment.save
+  rescue ActiveRecord::RecordNotFound
+    true
+  end
+end