Remove Stage name check on aggregate pipelines (#7237)

* add search for atlas search index

* added test for search in pipeline

* removed stage name check in pipeline

* removed spec for invalid query invalid key

* updated changelog

Co-authored-by: Diamond Lewis <findlewis@gmail.com>

src/Routers/AggregateRouter.js

@@ -4,38 +4,6 @@ import * as middleware from '../middlewares';
 import Parse from 'parse/node';
 import UsersRouter from './UsersRouter';
 
-const BASE_KEYS = ['where', 'distinct', 'pipeline', 'hint', 'explain'];
-
-const PIPELINE_KEYS = [
-  'addFields',
-  'bucket',
-  'bucketAuto',
-  'collStats',
-  'count',
-  'currentOp',
-  'facet',
-  'geoNear',
-  'graphLookup',
-  'group',
-  'indexStats',
-  'limit',
-  'listLocalSessions',
-  'listSessions',
-  'lookup',
-  'match',
-  'out',
-  'project',
-  'redact',
-  'replaceRoot',
-  'sample',
-  'skip',
-  'sort',
-  'sortByCount',
-  'unwind',
-];
-
-const ALLOWED_KEYS = [...BASE_KEYS, ...PIPELINE_KEYS];
-
 export class AggregateRouter extends ClassesRouter {
   handleFind(req) {
     const body = Object.assign(req.body, ClassesRouter.JSONFromQuery(req.query));
@@ -122,9 +90,6 @@ export class AggregateRouter extends ClassesRouter {
   }
 
   static transformStage(stageName, stage) {
-    if (ALLOWED_KEYS.indexOf(stageName) === -1) {
-      throw new Parse.Error(Parse.Error.INVALID_QUERY, `Invalid parameter for query: ${stageName}`);
-    }
     if (stageName === 'group') {
       if (Object.prototype.hasOwnProperty.call(stage[stageName], '_id')) {
         throw new Parse.Error(