将用户名更改为新用户名Django

我希望用户能够更改他的用户名，因为我尝试了这段代码，但它不起作用，任何人都可以帮助！

def edit(request):
    if request.method == 'POST':
        username = request.POST['username']
        password = request.POST['password']
        new_name = request.POST['new_name']
        user = authenticate(username=username,password=password)
        if user is not None:
            user = authenticate(username=new_name,password=password) 
            return redirect('userr')
    return render(request, 'index/edit.html')