Paypal refactor lib (#8420)

* Abstracted paypal logic from controller. Added intial tests

* Added checkout tests

* Added checkout success test

* Added subscribe test

* Added subscribeSuccess tests

* Added subscribeCancel tests

* Added ipn tests

* Fixed broken test

* Added integration tests and fixed linting issues

* Added errors for paypal checkout success integration test

* Removed extra test

* Removed pending status from subscribe cancel test

* Added more error checking and tests

* Fixed lint issues

website/common/locales/en/subscriber.json

@@ -154,5 +154,9 @@
     "noSudoAccess": "You don't have sudo access.",
     "couponCodeRequired": "The coupon code is required.",
     "eventRequired": "\"req.params.event\" is required.",
-    "countRequired": "\"req.query.count\" is required."
+    "countRequired": "\"req.query.count\" is required.",
+    "missingPaymentId": "Missing req.query.paymentId",
+    "missingCustomerId": "Missing req.query.customerId",
+    "missingPaypalBlock": "Missing req.session.paypalBlock",
+    "missingSubKey": "Missing req.query.sub"
 }