Add created_by to invoice and show it

db/migrate/20160217124256_add_created_by_user_id_to_invoice.rb

@@ -0,0 +1,5 @@
+class AddCreatedByUserIdToInvoice < ActiveRecord::Migration
+  def change
+    add_column :invoices, :created_by_user_id, :integer
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20150923190747) do
+ActiveRecord::Schema.define(version: 20160217124256) do
 
   create_table "article_categories", force: :cascade do |t|
     t.string "name",        limit: 255, default: "", null: false
@@ -166,6 +166,7 @@ ActiveRecord::Schema.define(version: 20150923190747) do
     t.decimal  "deposit_credit",               precision: 8, scale: 2, default: 0, null: false
     t.datetime "created_at"
     t.datetime "updated_at"
+    t.integer  "created_by_user_id"
   end
 
   add_index "invoices", ["delivery_id"], name: "index_invoices_on_delivery_id", using: :btree