uploads: mark uploads as failed if they're stuck processing for more than 4 hours.

test/jobs/prune_uploads_job_test.rb

@@ -0,0 +1,17 @@
+require 'test_helper'
+
+class PruneUploadsJobTest < ActiveJob::TestCase
+  context "PruneUploadsJob" do
+    should "prune expired uploads and media assets" do
+      upload = create(:upload, created_at: 6.hours.ago, status: "processing")
+      media_asset = create(:media_asset, created_at: 6.hours.ago, status: "processing")
+      upload_media_asset = create(:upload_media_asset, created_at: 6.hours.ago, media_asset: media_asset, upload: upload, status: "processing")
+
+      PruneUploadsJob.perform_now
+
+      assert_equal("error", upload.reload.status)
+      assert_equal("failed", upload_media_asset.reload.status)
+      assert_equal("failed", media_asset.reload.status)
+    end
+  end
+end