Update copier to generate a FormDocument

So that the draft is previewable.

Author: chao-xian

app/services/form_copy_service.rb

@@ -8,13 +8,15 @@ def copy
     copied_form = @form.dup
     copied_form.state = "draft"
     copied_form.external_id = nil
+    copied_form.submission_email = nil
     copied_form.group_form = GroupForm.new(group_id: @form.group.id, form_id: copied_form.id)
     copied_form.save!
 
     copy_pages(copied_form)
     copy_conditions_for_all_pages
 
     copied_form.reload
+    FormDocumentSyncService.update_draft_form_document(copied_form)
     copied_form
   end