added afterLogout trigger (#6217)

* added afterLogout trigger

* added verification of session object in tests

* removed obsolete code

* removed unsued code

* improved tests to verify user ID

src/Routers/UsersRouter.js

@@ -302,6 +302,7 @@ export class UsersRouter extends ClassesRouter {
                 records.results[0].objectId
               )
               .then(() => {
+                this._runAfterLogoutTrigger(req, records.results[0]);
                 return Promise.resolve(success);
               });
           }
@@ -311,6 +312,17 @@ export class UsersRouter extends ClassesRouter {
     return Promise.resolve(success);
   }
 
+  _runAfterLogoutTrigger(req, session) {
+    // After logout trigger
+    maybeRunTrigger(
+      TriggerTypes.afterLogout,
+      req.auth,
+      Parse.Session.fromJSON(Object.assign({ className: '_Session' }, session)),
+      null,
+      req.config
+    );
+  }
+
   _throwOnBadEmailConfig(req) {
     try {
       Config.validateEmailConfiguration({