CloudFront serving non-current version of CSS bundle file

[sean1588]

Problem description

We recently had an issue where new css styles were added and the site was missing the styles when deployed to pulumi.com. This ended up being due to CloudFront serving an older cached version of the css bundle file. Upon further investigation I built the site locally and genned the minified bundle and it turned up with the same css file name as the one currently on the site, with the same sha in the filename, even though the contents of the files were different. We should investigate how those file names are generated and how we can gen a different filename based on the file's contents. This will ensure that CloudFront won't serve the older version of the file from the cache.