added context to object save in JS SDK

Author: mtrezza

_includes/js/objects.md

@@ -199,6 +199,29 @@ teamMember.save(null, { cascadeSave: false });
 
 ```
 
+### Cloud Code context
+
+You may pass a `context` that is accessible in Cloud Code `beforeSave` and `afterSave` triggers for that `Parse.Object`. This is useful if you want to condition certain operations in Cloud Code triggers on ephemeral information that should not be saved with the `Parse.Object` in the database. The context is ephemeral in the sense that it vanishes after the Cloud Code triggers for that particular `Parse.Object` have executed. For example:
+
+```javascript
+var TeamMember = Parse.Object.extend("TeamMember");
+var teamMember = new TeamMember();
+teamMember.set("team", "A");
+
+var context = { notifyTeam: false };
+await teamMember.save(null, { context: context });
+```
+
+The context is then accessible in Cloud Code:
+
+```javascript
+Parse.Cloud.afterSave("TeamMember", async (req) => {
+    var notifyTeam = req.context.notifyTeam;
+    if (notifyTeam) {
+      // Notify team about new member.
+    }
+});
+```
 
 ## Retrieving Objects