Utility mixins for configuration forms.
A mixin for utilizing a registry to keep track of the pages and forms.
Objects using this mixin can have a dynamic list of forms, which can be updated by callers. New forms can be registered on them and existing forms can be removed. With this mixin, it is possible to extend a configuration page, allowing each form to load, validate, and save without the page hard-coding support for each form.
Add a form to the page.
Parameters: form_class (type) – The form to add to the page, as a subclass of