Add debug query string `origin` to invocations of the updateSubscription endpoint.

services/web/app/coffee/Features/Subscription/SubscriptionController.coffee

@@ -167,12 +167,13 @@ module.exports = SubscriptionController =
 				res.redirect "/user/subscription"
 
 	updateSubscription: (req, res, next)->
+		_origin = req?.query?.origin || null
 		AuthenticationController.getLoggedInUser req, (error, user) ->
 			return next(error) if error?
 			planCode = req.body.plan_code
 			if !planCode?
 				err = new Error('plan_code is not defined')
-				logger.err {user_id: user._id, err, planCode}, "[Subscription] error in updateSubscription form"
+				logger.err {user_id: user._id, err, planCode, origin: _origin, body: req.body}, "[Subscription] error in updateSubscription form"
 				return next(err)
 			logger.log planCode: planCode, user_id:user._id, "updating subscription"
 			SubscriptionHandler.updateSubscription user, planCode, null, (err)->

services/web/app/views/subscriptions/edit-billing-details.jade

@@ -19,7 +19,7 @@ block content
 		Recurly.config(!{recurlyConfig})
 		Recurly.buildBillingInfoUpdateForm({
 			target      : "#billingDetailsForm",
-			successURL  : "#{successURL}?_csrf=#{csrfToken}",
+			successURL  : "#{successURL}?_csrf=#{csrfToken}&origin=editBillingDetails",
 			signature   : "!{signature}",
 			accountCode : "#{user.id}"
 		});

services/web/public/coffee/main/subscription-dashboard.coffee

@@ -62,8 +62,7 @@ define [
 
 			$scope.inflight = true
 
-
-			$http.post(SUBSCRIPTION_URL, body)
+			$http.post("#{SUBSCRIPTION_URL}?origin=confirmChangePlan", body)
 				.success ->
 					location.reload()
 				.error ->
@@ -124,7 +123,7 @@ define [
 				plan_code: 'student'
 				_csrf : window.csrfToken
 			$scope.inflight = true
-			$http.post(SUBSCRIPTION_URL, body)
+			$http.post("#{SUBSCRIPTION_URL}?origin=downgradeToStudent", body)
 				.success ->
 					location.reload()
 				.error ->