Potentially add a feature to preserve existing URL params when filtering.

[jackrvan]

Originally discussed here https://groups.google.com/g/django-filter/c/loK3NN8mcqQ but Carlton mentioned we should move it here and said it would probably be a good addition to django-filter.We should try and plan out what this would look like. I am fairly new to Django but will start to look at the code here and see if there is anything I can figure out but if anyone has any experiences with doing something along these lines I think more feedback could be great in planning this out.

This is also related to the Stack overflow question here https://stackoverflow.com/questions/50265801/how-to-preserve-the-existing-query-string-when-submitting-a-form-in-django

[jackrvan]

I "fixed" this by adding this to my html file:

<input type="hidden" name="param1" id="id_param1" value="{{ param1 }}">
<input type="hidden" name="param2" id="id_param2" value="{{ param2 }}">
<input type="hidden" name="param3" id="id_param3" value="{{ param3 }}">

and this to my view:

    def get_context_data(self, **kwargs):
        context = super().get_context_data(**kwargs)
        context['param1'] = self.request.GET.get('param1', '')
        context['param2'] = self.request.GET.get('param2', '')
        context['param3'] = self.request.GET.get('param3', '')
        return context

I think it would still be nice if django-filter supported something like this in an easier way. Im not really sure still how it should behave though