如何在Django登录表单中自定义变量"next"？

from django import forms
from django.contrib.auth.forms import AuthenticationForm

class CustomLoginForm(AuthenticationForm):
    next = forms.CharField(widget=forms.HiddenInput, required=False)

from django.contrib.auth import authenticate, login
from django.shortcuts import render, redirect
from .forms import CustomLoginForm

def login_view(request):
    if request.method == 'POST':
        form = CustomLoginForm(request, data=request.POST)
        if form.is_valid():
            user = authenticate(request, username=form.cleaned_data.get('username'), password=form.cleaned_data.get('password'))
            if user is not None:
                login(request, user)
                next = form.cleaned_data.get('next')
                if next:
                    return redirect(next)
                else:
                    return redirect('some_default_view')
            else:
                # Return an 'invalid login' error message.
                pass
    else:
        form = CustomLoginForm(request)
    return render(request, 'login.html', {'form': form})

<form method="post" action="{% url 'login' %}">
  {% csrf_token %}
  {{ form.as_p }}
 <input type="hidden" name="next" value="{{ next }}" />
 <button type="submit">Login</button>
</form>