Adds context object in Cloud Code hooks (#4939)

* wip

* Refactors triggers a bit

- Adds testing for hooks and context

* comment nit

* nits

src/RestWrite.js

@@ -34,6 +34,7 @@ function RestWrite(config, auth, className, query, data, originalData, clientSDK
   this.clientSDK = clientSDK;
   this.storage = {};
   this.runOptions = {};
+  this.context = {};
   if (!query && data.objectId) {
     throw new Parse.Error(Parse.Error.INVALID_KEY_NAME, 'objectId is an invalid field name.');
   }
@@ -165,7 +166,7 @@ RestWrite.prototype.runBeforeTrigger = function() {
   }
 
   return Promise.resolve().then(() => {
-    return triggers.maybeRunTrigger(triggers.Types.beforeSave, this.auth, updatedObject, originalObject, this.config);
+    return triggers.maybeRunTrigger(triggers.Types.beforeSave, this.auth, updatedObject, originalObject, this.config, this.context);
   }).then((response) => {
     if (response && response.object) {
       this.storage.fieldsChangedByTrigger = _.reduce(response.object, (result, value, key) => {
@@ -1142,7 +1143,7 @@ RestWrite.prototype.runAfterTrigger = function() {
   this.config.liveQueryController.onAfterSave(updatedObject.className, updatedObject, originalObject);
 
   // Run afterSave trigger
-  return triggers.maybeRunTrigger(triggers.Types.afterSave, this.auth, updatedObject, originalObject, this.config)
+  return triggers.maybeRunTrigger(triggers.Types.afterSave, this.auth, updatedObject, originalObject, this.config, this.context)
     .catch(function(err) {
       logger.warn('afterSave caught an error', err);
     })