FIX: Add attachment content-disposition for all non-image files (PR #10058)

This will make it so the original filename is used when downloading all non-image files, bringing S3Store into line with the to_s3 migration and local storage. Video and audio files will still stream correctly in HTML players as well.

See https://meta.discourse.org/t/cannot-download-non-image-media-files-original-filenames-lost-when-uploaded-to-s3/152797 for a lot of extra context.

GitHub

This pull request has been mentioned on Discourse Meta. There might be relevant details there:

https://meta.discourse.org/t/cannot-download-non-image-media-files-original-filenames-lost-when-uploaded-to-s3/152797/12