Nullify deliveries and orders depending on an invoice (#718)

app/models/invoice.rb

@@ -4,8 +4,8 @@ class Invoice < ApplicationRecord
   belongs_to :supplier
   belongs_to :created_by, :class_name => 'User', :foreign_key => 'created_by_user_id'
   belongs_to :financial_link
-  has_many :deliveries
-  has_many :orders
+  has_many :deliveries, dependent: :nullify
+  has_many :orders, dependent: :nullify
 
   validates_presence_of :supplier_id
   validates_numericality_of :amount, :deposit, :deposit_credit

db/migrate/20181204000000_clear_invalid_invoices_from_orders.rb

@@ -0,0 +1,8 @@
+class ClearInvalidInvoicesFromOrders < ActiveRecord::Migration
+  class Order < ActiveRecord::Base; end
+  class Invoice < ActiveRecord::Base; end
+
+  def up
+    Order.where.not(invoice_id: Invoice.all).update_all(invoice_id: nil)
+  end
+end