FEATURE: Support private attachments when using S3 storage (#7677)

* Support private uploads in S3
* Use localStore for local avatars
* Add job to update private upload ACL on S3
* Test multisite paths
* update ACL for private uploads in migrate_to_s3 task

spec/requests/uploads_controller_spec.rb

@@ -285,12 +285,11 @@ describe UploadsController do
 
     context "prevent anons from downloading files" do
       it "returns 404 when an anonymous user tries to download a file" do
-        skip("this only works when nginx/apache is asset server") if Discourse::Application.config.public_file_server.enabled
         upload = upload_file("small.pdf", "pdf")
         delete "/session/#{user.username}.json"
 
         SiteSetting.prevent_anons_from_downloading_files = true
-        get upload.url
+        get "/uploads/#{site}/#{upload.sha1}.#{upload.extension}"
         expect(response.status).to eq(404)
       end
     end