FEATURE: add rake task that resets ACL on every object in S3

Some previous migrations to S3 may have bad ACLs set on objects. This
introduces a new rake task (`rake s3:correct_acl`) that will reset ACL on
every S3 object.

Vast majority of users will never have to run it, but if you have ACL issues
this is the atomic solution.

lib/tasks/s3.rake

@@ -101,6 +101,36 @@ def ensure_s3_configured!
   end
 end
 
+task 's3:correct_acl' => :environment do
+  ensure_s3_configured!
+
+  puts "ensuring public-read is set on every upload and optimized image"
+
+  i = 0
+
+  base_url = Discourse.store.absolute_base_url
+
+  objects = Upload.pluck(:id, :url).map { |array| array << :upload }
+  objects.concat(OptimizedImage.pluck(:id, :url).map { |array| array << :optimized_image })
+
+  puts "#{objects.length} objects found"
+
+  objects.each do |id, url, type|
+    i += 1
+    if !url.start_with?(base_url)
+      puts "Skipping #{type} #{id} since it is not stored on s3, url is #{url}"
+    else
+      key = url[(base_url.length + 1)..-1]
+      object = Discourse.store.s3_helper.object(key)
+      object.acl.put(acl: "public-read")
+    end
+    if i % 100 == 0
+      puts "#{i} done"
+    end
+  end
+
+end
+
 task 's3:upload_assets' => :environment do
   ensure_s3_configured!