json.extract!(
  plan_item,
  :id,
  :planned_type,
  :planned_id,
  :plan_on,
  :place_id,
  :start_at,
  :finish_at,
  :qrcode_url
)
json.plan_participants plan_item.plan_participants do |plan_participant|
  json.extract! plan_participant, :id, :participant_type, :participant_id
end
