Save the timestamp of the last mail to supplier and confirm resending it

db/migrate/20171001000000_add_last_sent_mail_to_order.rb

@@ -0,0 +1,5 @@
+class AddLastSentMailToOrder < ActiveRecord::Migration
+  def change
+    add_column :orders, :last_sent_mail, :datetime
+  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: 20170801000000) do
+ActiveRecord::Schema.define(version: 20171001000000) do
 
   create_table "article_categories", force: :cascade do |t|
     t.string "name",        limit: 255, default: "", null: false
@@ -243,6 +243,7 @@ ActiveRecord::Schema.define(version: 20170801000000) do
     t.datetime "boxfill"
     t.date     "pickup"
     t.integer  "invoice_id"
+    t.datetime "last_sent_mail"
   end
 
   add_index "orders", ["state"], name: "index_orders_on_state", using: :btree