get next url form request

    order: POST.next GET.next HTTP_REFERER, default_next

def request_get_next(request, default_next):
    """
    get next url form request

    order: POST.next GET.next HTTP_REFERER, default_next
    """
    next_url = request.POST.get('next')\
        or request.GET.get('next')\
        or request.META.get('HTTP_REFERER')\
        or default_next
    return next_url