Extracted from django-fluent-pages, ready for other apps too.
The polymorphic admin is implemented via a parent admin for the base
model, and separate admin interfaces for the child models.
The parent model needs to inherit PolymorphicParentModelAdmin,
and override `get_admin_for_model()` and `get_child_model_classes()`
to find the child admin interfaces.
The derived models have their own `ModelAdmin` class, which inherits
from `PolymorphicChildModelAdmin`. The parent admin redirects it's
change and delete views to the child admin.
By adding `polymorphic` to the INSTALLED_APPS, the breadcrumbs will be
fixed as well, to remain unchanged between the child applications.
Since the original author disappeared, this commit marks the line between what
he did and what enhancements we (the community of maintainers) bring to the
project.
Chris Glass
Diederik van der Boor
Christopher Glass
Bert Constantin