Improve type hints for UserSerializer

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

@@ -1,10 +1,18 @@
+from __future__ import annotations
+
+import typing
+
 from django.contrib.auth import get_user_model
 from rest_framework import serializers
 
+if typing.TYPE_CHECKING:
+    from {{ cookiecutter.project_slug }}.users.models import User as UserType
+
+
 User = get_user_model()
 
 
-class UserSerializer(serializers.ModelSerializer):
+class UserSerializer(serializers.ModelSerializer[UserType]):
     class Meta:
         model = User
         {%- if cookiecutter.username_type == "email" %}