uploads: use storage manager to distribute files.

Refactors the upload process to pass around temp files, rather than
passing around file paths and directly writing output to the local
filesystem. This way we can pass the storage manager the preview /
sample / original temp files, so it can deal with storage itself.

* Change Download::File#download! to return a temp file.

* Change DanbooruImageResizer and PixivUgoiraConverter to accept/return
  temp files instead of file paths.

* Change Upload#generate_resizes to return temp files for previews and samples.

* Change Upload#generate_resizes to generate ugoira .webm samples
  synchronously instead of asynchronously.

app/logical/pixiv_ugoira_service.rb

@@ -1,32 +1,10 @@
 class PixivUgoiraService
   attr_reader :width, :height, :frame_data, :content_type
 
-  def self.regen(post)
-    service = new()
-    service.load(
-      :is_ugoira => true,
-      :ugoira_frame_data => post.pixiv_ugoira_frame_data.data
-    )
-    service.generate_resizes(post.file_path, post.large_file_path, post.preview_file_path, false)
-  end
-
   def save_frame_data(post)
     PixivUgoiraFrameData.create(:data => @frame_data, :content_type => @content_type, :post_id => post.id)
   end
 
-  def generate_resizes(source_path, output_path, preview_path, delay = true)
-    # Run this a bit in the future to give the upload process time to move the file
-    if delay
-      PixivUgoiraConverter.delay(:queue => Socket.gethostname, :run_at => 10.seconds.from_now, :priority => -1).convert(source_path, output_path, preview_path, @frame_data)
-    else
-      PixivUgoiraConverter.convert(source_path, output_path, preview_path, @frame_data)
-    end
-
-    # since the resizes will be delayed, just touch the output file so the
-    # file distribution wont break
-    FileUtils.touch([output_path, preview_path])
-  end
-
   def calculate_dimensions(source_path)
     folder = Zip::File.new(source_path)
     tempfile = Tempfile.new("ugoira-dimensions")