old_contents: from core.models.user import AtmosphereUser
  from rest_framework import serializers
  
  
  class UserSerializer(serializers.HyperlinkedModelSerializer):
      class Meta:
          model = AtmosphereUser
          view_name = 'api_v2:atmosphereuser-detail'
          fields = ('id', 'url', 'username', 'first_name', 'last_name', 'email', 'is_staff', 'is_superuser')
  
new_contents: from core.models.user import AtmosphereUser
  from rest_framework import serializers
  
  
  class UserSerializer(serializers.HyperlinkedModelSerializer):
      class Meta:
          model = AtmosphereUser
          view_name = 'api_v2:atmosphereuser-detail'
          fields = ('id', 'url', 'username', 'first_name', 'last_name', 'email', 'is_staff', 'is_superuser', 'date_joined')
  
subject: add date joined to user serializer