Wagtail Forms - Upload Image Field - Override the Serve Method

models.py

class FormPage(AbstractEmailForm):
    form_builder = ExtendedFormBuilder # see the step above

    def serve(self, request, *args, **kwargs):
        if request.method == 'POST':
            # form = self.get_form(request.POST, page=self, user=request.user)  # Original line
            form = self.get_form(request.POST, request.FILES, page=self, user=request.user)

            if form.is_valid():
                self.process_form_submission(form)
                return render(
                    request,
                    self.get_landing_page_template(request),
                    self.get_context(request)
                )
        else:
            form = self.get_form(page=self, user=request.user)

        context = self.get_context(request)
        context['form'] = form
        return render(
            request,
            self.get_template(request),
            context
        )
    
    # the rest of the form page definition ...