Switch from unmaintained paperclip to kt-paperclip (#16724)

* 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.

Gemfile

@@ -20,7 +20,7 @@ gem 'dotenv-rails', '~> 2.7'
 gem 'aws-sdk-s3', '~> 1.103', require: false
 gem 'fog-core', '<= 2.1.0'
 gem 'fog-openstack', '~> 0.3', require: false
-gem 'paperclip', '~> 6.0'
+gem 'kt-paperclip', '~> 7.0'
 gem 'blurhash', '~> 0.1'
 
 gem 'active_model_serializers', '~> 0.10'