V3 payments 6 (#7104)

* payments api: cancelSubscription

* some more tests for amazon payments

* promisifying amazon payments

* somehow payment stub is not working

* cleaning up tests

* renaming tests in api/v3/integration/payments

* improvements

* cleanup, lint

* fixes as per comments

* moment.zone() is back in.

test/api/v3/integration/payments/POST-payments_amazon_subscribe.test.js

@@ -0,0 +1,21 @@
+import {
+  generateUser,
+  translate as t,
+} from '../../../../helpers/api-integration/v3';
+
+describe('payments - amazon - #subscribe', () => {
+  let endpoint = '/payments/amazon/subscribe';
+  let user;
+
+  beforeEach(async () => {
+    user = await generateUser();
+  });
+
+  it('verifies subscription code', async () => {
+    await expect(user.post(endpoint)).to.eventually.be.rejected.and.eql({
+      code: 400,
+      error: 'BadRequest',
+      message: t('missingSubscriptionCode'),
+    });
+  });
+});