In uploads, claim MIME `audio/flac` instead of `audio/x-flac`; `audio/vnd.wave` instead of `audio/x-wav`; possibly more

[chrisbobbe]

See discussion: #issues > flutter client maps .flac to `audio/x-flac` MIME type @ 💬

package:mime uses deprecated MIME types x-*:

• Don't use x-* MIME types when possible dart-lang/tools#588
• Create process for adding MIME-types to mapping. dart-lang/tools#2028

Sounds like we should probably add a workaround in our own code in the Flutter app, where if the stdlib tells us the MIME type is audio/x-flac we translate that to audio/flac instead.

This will become important with #2179 because the server won't accept the x-* variant as cause for rendering inline-audio-player content.

Implementation

Pending the upstream issues linked above, package:mime's docs mention a way to make a custom resolver that overrides the default resolution. We should try that.