* Switch from unmaintained paperclip to kt-paperclip

* Drop some compatibility monkey-patches not required by kt-paperclip

* Drop media spoof check monkey-patching

It's broken with kt-paperclip and hopefully it won't be needed anymore

* Fix regression introduced by paperclip 6.1.0

* Do not rely on pathname to call FastImage

* Add test for ogg vorbis file with cover art

* Add audio/vorbis to the accepted content-types

This seems erroneous as this would be the content-type for a vorbis stream
without an ogg container, but that's what the `marcel` gem outputs, so…

* Restore missing for_as_default method

* Refactor Attachmentable concern and delay Paperclip's content-type spoof check

Check for content-type spoofing *after* setting the extension ourselves, this
fixes a regression with kt-paperclip's validations being more strict than
paperclip 6.0.0 and rejecting some Pleroma uploads because of unknown
extensions.

* Please CodeClimate

* Add audio/vorbis to the unreliable set

It doesn't correspond to a file format and thus has no extension associated.

* Fix media processing getting stuck on too much stdin/stderr

See thoughtbot/terrapin#5

* Remove dependency on paperclip-av-transcoder gem

* Remove dependency on streamio-ffmpeg gem

* Disable stdin on ffmpeg process

* Optimize map { ... }.compact

using Enumerable#filter_map, supported since Ruby 2.7

* Add poyfill for Enumerable#filter_map

- Change audio files to not be stripped of metadata
- Automatically extract cover art from audio if it exists
- Add `thumbnail` parameter to `POST /api/v1/media`, `POST /api/v2/media` and `PUT /api/v1/media/:id`
- Add `icon` to represent it in attachments in ActivityPub
- Fix `preview_url` containing URL of missing missing image when there is no thumbnail instead of null
- Fix duration of audio not being displayed on public pages until the file is loaded

Fix #13403

Change `tootctl media lookup` to not use an interactive prompt

Fix #9106