Why is request.user is anonymous in Django RedirectView?

Question

There are a lot of questions similar to this one, but none quite capture the situation I am in. I am coding a Django/ React app and I have integrated with Spotify. Currently, on the Django side of things I have the user getting redirected back to their profile page after connecting to Spotify. This is done hardcoding the URL with the http response redirect:

class SpotifyCallbackView(RedirectView):

    def handle_callback(self, request):
        print(self.request.META)
        if request.GET.get("refresh_token", False):
            refresh_token = request.GET["refresh_token"]

        code = request.GET["code"]
        if request.GET.get("refresh_token", False):

            response = requests.post(
                "https://accounts.spotify.com/api/token",
                data={
                    "grant_type": "refresh_token",
                    "refresh_token": refresh_token,

                },
                headers=AUTH_HEADER,
            )
            return response.json()

        else:
            response = requests.post(
                "https://accounts.spotify.com/api/token",
                data={
                    "grant_type": "authorization_code",
                    "code": code,
                    "redirect_uri": request.build_absolute_uri("callback"),

                },
                headers=AUTH_HEADER,
            )
            return response.json()

    def get(self, request, *args, **kwargs):
    
        auth_items = self.handle_callback(request)
        access_token = auth_items["access_token"]
        if "refresh_token" in auth_items.keys():
            refresh_token = auth_items["refresh_token"]
        else:
            refresh_token = ""

        if refresh_token != "":
            return HttpResponseRedirect('http://localhost:3000/users/1/' + access_token + '/' + refresh_token)
        else:
            return HttpResponse(access_token)

Obviously, the user's ID is not always going to be "1" so I want to be able to grab that ID from somewhere, and after some searching I saw that I can grab that info from self.request.user, except I can't. It's anonymous. Why is this the case? I am using Django Knox for Authentication and Django's built in User model btw. Is there another way to grab this ID?