On page 292, we create a SupportRequest model that belongs_to Order
class SupportRequest < ApplicationRecord
belongs_to :order, optional: true
end
We also need to add the has_many end of the relationship to orders or else you will get a foreign key error when you attempt to destroy an Order that has a SupportRequest associated with that order id.
class Order < ApplicationRecord
has_many :line_items, dependent: :destroy
# need this relationship defined or it will break orders#destroy
# since the relationship is optional on the SupportRequest end, it should nullify
has_many :support_requests, dependent: :nullify
# rest of class
end