Fix attachment not being re-downloaded even if file is not stored (#12125)

Change the behaviour of remotable concern. Previously, it would skip
downloading an attachment if the stored remote URL is identical to
the new one. Now it would not be skipped if the attachment is not
actually currently stored by Paperclip.

app/controllers/api/v1/streaming_controller.rb

@@ -5,11 +5,17 @@ class Api::V1::StreamingController < Api::BaseController
 
   def index
     if Rails.configuration.x.streaming_api_base_url != request.host
-      uri = URI.parse(request.url)
-      uri.host = URI.parse(Rails.configuration.x.streaming_api_base_url).host
-      redirect_to uri.to_s, status: 301
+      redirect_to streaming_api_url, status: 301
     else
-      raise ActiveRecord::RecordNotFound
+      not_found
     end
   end
+
+  private
+
+  def streaming_api_url
+    Addressable::URI.parse(request.url).tap do |uri|
+      uri.host = Addressable::URI.parse(Rails.configuration.x.streaming_api_base_url).host
+    end.to_s
+  end
 end