* Drop end-of-life Django versions, add Django 2.2 and 3.0, and Python 3.8 (johnthagen)
0.5.4
* Update UniqueFieldsMixin to support DRF 3.11 validator context API (mands)
0.5.3
* Support custom resource_type_field_name for polymorphic serialize (tsaipoan)
0.5.2
* Feature: Enable support for nested polymorphic relations 81 (csdenboer)
0.5.1
* Fix: Validate nested field before creating it even in partial update (yuekui) * Fix some potential issues in the delete phase for reverse relations update