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.

app/models/preview_card.rb

@@ -27,6 +27,8 @@
 #
 
 class PreviewCard < ApplicationRecord
+  include Attachmentable
+
   IMAGE_MIME_TYPES = ['image/jpeg', 'image/png', 'image/gif'].freeze
   LIMIT = 1.megabytes
 
@@ -41,9 +43,7 @@ class PreviewCard < ApplicationRecord
 
   has_and_belongs_to_many :statuses
 
-  has_attached_file :image, processors: [:thumbnail, :blurhash_transcoder], styles: ->(f) { image_styles(f) }, convert_options: { all: '-quality 80 -strip' }
-
-  include Attachmentable
+  has_attached_file :image, processors: [:thumbnail, :blurhash_transcoder], styles: ->(f) { image_styles(f) }, convert_options: { all: '-quality 80 -strip' }, validate_media_type: false
 
   validates :url, presence: true, uniqueness: true
   validates_attachment_content_type :image, content_type: IMAGE_MIME_TYPES