Add missing factories for affirm payments
user
```ruby
FactoryBot.define do
  factory :affirm_payment, class: Spree::Payment do
    source_type "SolidusAffirm::Checkout"
    state 'checkout'
  end

  factory :captured_affirm_payment, class: Spree::Payment do
    payment_method { create(:affirm_payment_gateway) }
    source { create(:affirm_checkout) }
    response_code "123456789"
  end
end
```
assistant