feat: mongodb driver 4.x (#9832)

* feat: mongodb driver 4.x

* feat: up dbsearach

install/package.json

@@ -78,14 +78,14 @@
         "material-design-lite": "^1.3.0",
         "mime": "^2.5.2",
         "mkdirp": "^1.0.4",
-        "mongodb": "3.7.1",
+        "mongodb": "4.1.2",
         "morgan": "^1.10.0",
         "mousetrap": "^1.6.5",
         "multiparty": "4.2.2",
         "@nodebb/bootswatch": "3.4.2",
         "nconf": "^0.11.2",
         "nodebb-plugin-composer-default": "7.0.7",
-        "nodebb-plugin-dbsearch": "5.0.3",
+        "nodebb-plugin-dbsearch": "5.0.5",
         "nodebb-plugin-emoji": "^3.5.0",
         "nodebb-plugin-emoji-android": "2.0.5",
         "nodebb-plugin-markdown": "8.14.3",

src/database/mongo/connection.js

@@ -44,10 +44,9 @@ connection.getConnectionString = function (mongo) {
 connection.getConnectionOptions = function (mongo) {
 	mongo = mongo || nconf.get('mongo');
 	const connOptions = {
-		poolSize: 10,
+		maxPoolSize: 10,
+		minPoolSize: 3,
 		connectTimeoutMS: 90000,
-		useNewUrlParser: true,
-		useUnifiedTopology: true,
 	};
 
 	return _.merge(connOptions, mongo.options || {});