[Python] django rest framework serializer read_only_fields does not work

I am using django rest framework to create a blog website for fun. I am using neon db for the database. I have a users model in which I have a created_at attribute with datetimetz datatype. I have also set the default value to NOW() and in the serializer i have set the attribute to read_only_fields. But when i'm doing a post request to create a new user, it puts in null in the field and the created_at is filled as null in the database table.

My users model:

class Users(models.Model):
user_id = models.AutoField(primary_key=True,null=False,blank=True)
username = models.CharField(max_length=100)
email = models.CharField(max_length=254)
password_hash = models.CharField(max_length=30, blank=True, null=True)
created_at = models.DateTimeField(null=False,blank=True)

class Meta:
managed = False
db_table = 'users'


my serializer:

class UserSerializer(serializers.ModelSerializer):
class Meta:
model = Users
read_only_fields = ('created_at',)
fields = '__all__'


my view :

class UsersList(APIView):
"""
get all users or create a single user
"""
def get(self, request, format=None):
users = Users.objects.all()
serializer = UserSerializer(users,many=True)
return Response(serializer.data,status=status.HTTP_200_OK)

def post(self, request, format=None):
serializer = UserSerializer(data = request.data)
if serializer.is_valid():
serializer.save()
return Response(serializer.data,status=status.HTTP_201_CREATED)
return Response(serializer.errors, status=status.HTTP_400_BAD_REQUEST)


i have tried this:

class UserSerializer(serializers.ModelSerializer):
created_at = serializers.SerializerMethodField()
class Meta:
model = Users
read_only_fields = ('created_at',)
fields = '__all__'

def get_created_at(self, instance):
return instance.created_at.strftime("%B %d %Y")



it didn't work plus i don't want to do this. i want DRF to NOT include the created_at field and let the neon db table set the default value for the field.

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