How to handle attachments with identical digests on a single post

[quentez]

Is a post allowed to have two attachments with the same digest but different names? Imagine an app that would allow for a user to pick an avatar and a profile background, storing both in the same post with a different name for each, nothing prevents the user from picking the same file twice.

This becomes more problematic if apps are allowed to publish posts with attachments with different content_type but same digest: In that case, what Content-Type should the attachment endpoint use when returning an attachment?