[WIP] Amazon refactor to lib (#8403)

* Moved amazon tests to folder

* Abstracted amazon payment code and added initial test

* Abstracted cancel and subscribe logic to amazon payment lib

* Added arg checks to checkout

* Added constants. Added more subscription test

* Added with arg checks to cancel

* Fixed linting issues

* Added integration tests for amazon subscribe cancel

* Added integration test for amazon checkout

* Added integration test for amazon subscribe

* Added coupon unit test

* Fixed lint

* Fixed minor test issue and changed header expectations

* Fixed line endings

test/api/v3/integration/payments/amazon/POST-payments_amazon_createOrderReferenceId.test.js

@@ -0,0 +1,20 @@
+import {
+  generateUser,
+} from '../../../../../helpers/api-integration/v3';
+
+describe('payments - amazon - #createOrderReferenceId', () => {
+  let endpoint = '/amazon/createOrderReferenceId';
+  let user;
+
+  beforeEach(async () => {
+    user = await generateUser();
+  });
+
+  it('verifies billingAgreementId', async () => {
+    await expect(user.post(endpoint)).to.eventually.be.rejected.and.eql({
+      code: 400,
+      error: 'BadRequest',
+      message: 'Missing req.body.billingAgreementId',
+    });
+  });
+});