add acts_as_paranoid to voucher

This is so the relation
`belongs_to :originator, -> { with_deleted }, polymorphic: true`
setup in Spree::Adjustement works as expected.

app/models/voucher.rb

@@ -1,6 +1,8 @@
 # frozen_string_literal: false
 
 class Voucher < ApplicationRecord
+  acts_as_paranoid
+
   include CalculatedAdjustments
 
   belongs_to :enterprise

db/migrate/20230315040748_add_deleted_at_to_vouchers.rb

@@ -0,0 +1,6 @@
+class AddDeletedAtToVouchers < ActiveRecord::Migration[6.1]
+  def change
+    add_column :vouchers, :deleted_at, :datetime
+    add_index :vouchers, :deleted_at
+  end
+end

db/schema.rb

@@ -1196,7 +1196,9 @@ ActiveRecord::Schema[7.0].define(version: 2023_04_24_141213) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.bigint "enterprise_id"
+    t.datetime "deleted_at"
     t.index ["code", "enterprise_id"], name: "index_vouchers_on_code_and_enterprise_id", unique: true
+    t.index ["deleted_at"], name: "index_vouchers_on_deleted_at"
     t.index ["enterprise_id"], name: "index_vouchers_on_enterprise_id"
   end