feat(promotion code): Promotion code system done

I added the features for users to use promotion code
and for promoters to create on their events.
May be rewrite to discount code?

db/migrate/20250823170409_create_orders.rb

@@ -1,14 +1,15 @@
 class CreateOrders < ActiveRecord::Migration[8.0]
   def change
     create_table :orders do |t|
-      t.references :user, null: false, foreign_key: false
-      t.references :event, null: false, foreign_key: false
       t.string :status, null: false, default: "draft"
       t.integer :total_amount_cents, null: false, default: 0
       t.integer :payment_attempts, null: false, default: 0
       t.timestamp :expires_at
       t.timestamp :last_payment_attempt_at
 
+      t.references :user, null: false, foreign_key: false
+      t.references :event, null: false, foreign_key: false
+
       t.timestamps
     end