Fix canse insesitive of Users.findOneByUsername

packages/rocketchat-lib/server/models/Users.js

@@ -21,9 +21,11 @@ class ModelUsers extends RocketChat.models._Base {
 	}
 
 	findOneByUsername(username, options) {
-		const query = {
-			username: new RegExp(username, 'i')
-		};
+		if (typeof username === 'string') {
+			username = new RegExp(username, 'i')
+		}
+
+		const query = {username};
 
 		return this.findOne(query, options);
 	}