Create SolidusAfterpay::PaymentSource

To keep track of the checkout with Afterpay and the Payment in Solidus we
need a model that will be the Source of the Payment when payed with the
Afterpay PaymentMethod.

app/models/solidus_afterpay/payment_source.rb

@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+module SolidusAfterpay
+  class PaymentSource < SolidusSupport.payment_source_parent_class
+    self.table_name = 'solidus_afterpay_payment_sources'
+
+    validates :token, presence: true
+  end
+end

db/migrate/20210813142725_create_solidus_afterpay_payment_sources.rb

@@ -0,0 +1,12 @@
+class CreateSolidusAfterpayPaymentSources < SolidusSupport::Migration[4.2]
+  def change
+    create_table :solidus_afterpay_payment_sources do |t|
+      t.string :token
+      t.references :payment_method, index: true
+
+      t.timestamps
+    end
+
+    add_foreign_key :solidus_afterpay_payment_sources, :spree_payment_methods, column: :payment_method_id
+  end
+end