FEATURE: Add S3 etag value to uploads table (#6795)

db/migrate/20181218071253_add_etag_to_uploads.rb

@@ -0,0 +1,9 @@
+class AddEtagToUploads < ActiveRecord::Migration[5.2]
+  def change
+    add_column :uploads, :etag, :string
+    add_index :uploads, [:etag]
+
+    add_column :optimized_images, :etag, :string
+    add_index :optimized_images, [:etag]
+  end
+end