core/app/models/spree/store_payment_method.rb
module Spree
class StorePaymentMethod < Spree::Base
self.table_name = 'spree_payment_methods_stores'
belongs_to :store, class_name: 'Spree::Store', touch: true
belongs_to :payment_method, class_name: 'Spree::PaymentMethod', touch: true
validates :store, :payment_method, presence: true
validates :store_id, uniqueness: { scope: :payment_method_id }
end
end