i want to convert site 5.6 to 5.7 version. How to upgrade custom package 5.6 to 5.7 version
this is my package structure
Pacakge
->tony_mailing_list (Main Folder)
-> blocks
-> controllers
-> images
-> js
-> languages
-> models
-> single_pages
-> tools
-> controller.php

i want to move this plugin 5.6 to 5.7.

Class 'GroupSearch' not found