Add Note class to memo about backup files.

app/models/fluentd/setting_archive/note.rb

@@ -0,0 +1,17 @@
+class Fluentd
+  module SettingArchive
+    class Note
+      include Archivable
+
+      FILE_EXTENSION = ".note".freeze
+
+      def self.find_by_file_id(backup_dir, file_id)
+        new(file_path_of(backup_dir, file_id))
+      end
+
+      def initialize(file_path)
+        @file_path = file_path
+      end
+    end
+  end
+end