form_duplicator.rb

old_form_id = # OLD FORM ID
new_form_id = # NEW FORM ID

old_form = FormTemplate.find(old_form_id)
new_form = FormTemplate.find(new_form_id)

old_form.form_template_items.each do |old_item|
  attributes = old_item.attributes
  attributes.delete("id")
  attributes["form_template_id"] = new_form_id

  FormTemplateItem.where(attributes).first_or_create
end
Team.where(form_template_id: old_form_id).update_all(form_template_id: new_form_id)