After adding new class:
composer dumpautoload -o
Composer Autoloading within WordPress Plugin - Oct 15, 2019
WordPress has no concept of a shared library. If you’re using Composer packages also used in other plugins, your version may not be the one loaded. To work around this issue you can rename the package namespace.
These notes were done in winter 2020.
Composes all dependencies as a package inside a WordPress plugin. Load packages through Composer and have them wrapped inside your own namespace.
Composer plugin that wraps all composer vendor packages inside your own namespace. Intended for WordPress plugins.
More fire and forget than Mozart, uses composer hooks
Also available in a version not tied into composer hooks