I've created a Drupal 8 module that adds a custom plugin to the core's CKEditor. This plugin allows users to add tabbed content to their pages.
The problem is that the plugin adds a class to the element it creates and CKEditor by default removes classes from most elements once you save the node.
I can change CKEditor config for Basic HTML editor (admin/config/content/formats/manage/basic_html) to allow classes in elements by changing to in "Allowed HTML tags" input.
Now I would love to be able to do this programmatically somehow. How can I change the configuration for CKEditor in a Drupal module? Especially the "extraAllowedContent" config value.
The project for reference purposes can be found at https://github.com/j-vee/ckeditor_tabber