Support for multitable inherited models. #30
Description
Currently permanent does not work with inherited models.
If the parent model is permanent e.g.
class A(PermanentModel):
...
class B(A):
....
class C(A):
....listing and such will fail due to the child models not having the removed field.
Having the child models permanent will instead cause issues when deleting as only the child models are being soft deleted, the parent object will still be hard deleted leading to a constraint violation. Attempting to inherit permanent in both parent and child models will also result in a clash of the removed field.