Having a server with Samba providing AD and Domain Controller functionality will provide you with a very mature and professional way to have a centralized place with all users and groups information. It will free you from the burden of having to manage users and groups on each server. This solution is useful for authenticating applications such as WordPress, FTP servers, HTTP servers, you name it.
This step-by-step tutorial about setting up Samba as an AD and Domain Controller will demonstrate to you how you can achieve this solution for your network, servers, and applications.