Refactored stripe checkout (#10345)

* Refactored stripe checkout

* Fixed dependency injection cache

website/server/libs/payments/stripe/api.js

@@ -0,0 +1,14 @@
+import stripeModule from 'stripe';
+import nconf from 'nconf';
+
+let stripe = stripeModule(nconf.get('STRIPE_API_KEY'));
+
+function setStripeApi (stripeInc) {
+  stripe = stripeInc;
+}
+
+function getStripeApi () {
+  return stripe;
+}
+
+module.exports = { getStripeApi, setStripeApi };