I have a multi-site setup and am planning on using Amazon S3 as a CDN. I set up my bucket and put in my CDN credentials. When I go to a blog and hit the Upload Attachments button, it uploads all the files to the correct bucket, but just in the /files directory. Each site uploads into this same directory, and they don't recreate the blogs.dir/<blog_id>/files structure. How can I maintain separation of blog files in the CDN?