Fix audio-only OGG and WebM files not being processed as such (#11151)

Also, because Chrome sends audio/mp3 instead of audio/mpeg as it's
supposed to, we need to whitelist that mime type as well

app/models/concerns/attachmentable.rb

@@ -10,10 +10,21 @@ module Attachmentable
   included do
     before_post_process :set_file_extensions
     before_post_process :check_image_dimensions
+    before_post_process :set_file_content_type
   end
 
   private
 
+  def set_file_content_type
+    self.class.attachment_definitions.each_key do |attachment_name|
+      attachment = send(attachment_name)
+
+      next if attachment.blank? || attachment.queued_for_write[:original].blank?
+
+      attachment.instance_write :content_type, calculated_content_type(attachment)
+    end
+  end
+
   def set_file_extensions
     self.class.attachment_definitions.each_key do |attachment_name|
       attachment = send(attachment_name)
@@ -47,4 +58,10 @@ module Attachmentable
 
     extension
   end
+
+  def calculated_content_type(attachment)
+    Paperclip.run('file', '-b --mime :file', file: attachment.queued_for_write[:original].path).split(/[:;\s]+/).first.chomp
+  rescue Terrapin::CommandLineError
+    ''
+  end
 end

app/models/media_attachment.rb

@@ -31,9 +31,9 @@ class MediaAttachment < ApplicationRecord
   AUDIO_FILE_EXTENSIONS = ['.ogg', '.oga', '.mp3', '.wav', '.flac', '.opus'].freeze
 
   IMAGE_MIME_TYPES             = ['image/jpeg', 'image/png', 'image/gif', 'image/webp'].freeze
-  VIDEO_MIME_TYPES             = ['video/webm', 'video/mp4', 'video/quicktime'].freeze
+  VIDEO_MIME_TYPES             = ['video/webm', 'video/mp4', 'video/quicktime', 'video/ogg'].freeze
   VIDEO_CONVERTIBLE_MIME_TYPES = ['video/webm', 'video/quicktime'].freeze
-  AUDIO_MIME_TYPES             = ['audio/wave', 'audio/wav', 'audio/x-wav', 'audio/x-pn-wave', 'audio/ogg', 'audio/mpeg', 'audio/webm', 'audio/flac'].freeze
+  AUDIO_MIME_TYPES             = ['audio/wave', 'audio/wav', 'audio/x-wav', 'audio/x-pn-wave', 'audio/ogg', 'audio/mpeg', 'audio/mp3', 'audio/webm', 'audio/flac'].freeze
 
   BLURHASH_OPTIONS = {
     x_comp: 4,