ValueError: Cannot assign “”: “Message.name” must be a “CustomUser” instance

You can’t just pass a string and reference it to an object of CustomUser class. You’ll have to pass an instance of it. First get the relevant instance by using id or a suitable unique attribute,(hope the name is unique)

def get_object(self, name):
    return CustomUser.objects.get(name=name)

And then pass it in your save_message(self, name, message) method,

def save_message(self, name, message):
    user_obj = self.get_object(name)
    Message.objects.create(name=user_obj, content=message)