Add djangorestframework-stubs

Add djangorestframework-stubs to local.txt requirements
Modify setup.cfg to add stubs to mypy settings
Fix new type error in DRF

`./users/api/views.py:19: error: Incompatible type for lookup 'id': (got "Union[AutoField[Union[Combinable, int, str], int], Any]", expected "Union[str, int]")`

by asserting that `self.request.user.id` is an int

{{cookiecutter.project_slug}}/requirements/local.txt

@@ -17,6 +17,9 @@ mypy==0.910  # https://github.com/python/mypy
 django-stubs==1.8.0  # https://github.com/typeddjango/django-stubs
 pytest==6.2.5  # https://github.com/pytest-dev/pytest
 pytest-sugar==0.9.4  # https://github.com/Frozenball/pytest-sugar
+{%- if cookiecutter.use_drf == "y" %}
+djangorestframework-stubs==1.4.0  # https://github.com/typeddjango/djangorestframework-stubs
+{%- endif %}
 
 # Documentation
 # ------------------------------------------------------------------------------

{{cookiecutter.project_slug}}/setup.cfg

@@ -24,7 +24,7 @@ ignore_missing_imports = True
 warn_unused_ignores = True
 warn_redundant_casts = True
 warn_unused_configs = True
-plugins = mypy_django_plugin.main
+plugins = mypy_django_plugin.main{% if cookiecutter.use_drf == "y" %}, mypy_drf_plugin.main{% endif %}
 
 [mypy.plugins.django-stubs]
 django_settings_module = config.settings.test

{{cookiecutter.project_slug}}/{{cookiecutter.project_slug}}/users/api/views.py

@@ -16,6 +16,7 @@ class UserViewSet(RetrieveModelMixin, ListModelMixin, UpdateModelMixin, GenericV
     lookup_field = "username"
 
     def get_queryset(self, *args, **kwargs):
+        assert isinstance(self.request.user.id, int)
         return self.queryset.filter(id=self.request.user.id)
 
     @action(detail=False, methods=["GET"])