The User hash module allows you to create an individual hash for each user. Use it as a light-weight user identification where you do not want to use the Drupal login credentials. E.g.
Module
What's known as plugin or addon in other platforms, is what we call a module in the Drupal universe. Drupal core itself is a a collection of modules as well and the community has added and maintains tens of thousands of individual modules on top of that.