Add a 10% discount if the customer is tagged as 'vip'

vip_customer_discount.rb

is_vip = false
Input.customer.tags.each {|tag| is_vip = true if tag.name == "vip"}
return unless is_vip

Input.cart.line_items.each do |line_item|
  product = line_item.variant.product
  next if product.gift_card?
  line_item.change_line_price(line_item.price * .9, message: "VIP Discount Applied!")
end

Output.cart = Input.cart