docs: def simple_contact(request, username=""):
      """
      Defines simple contact form that can be used to
      contact a site member passed by username in the URL
      or to all superusers or to a list defined in settings.DEFAULT_CONTACTS.
      """
      site = Site.objects.get_current()
      form = ContactForm(request.POST or None)
      UserModel = get_user_model()
      recipients = []
      site_form = False
  
      logger.debug('Recipients should be empty: %s' % recipients)
  
      # if we know, fill in the user name and email
      if request.user.is_authenticated:
          # first, resolve username for tango and non-tango sites
          try:
              name = request.user.display_name
          except AttributeError:
              name = request.user.username
          form.fields['sender_name'].widget.attrs['readonly'] = 'true'
          form.fields['sender_name'].initial = name
          form.fields['sender_email'].widget.attrs['readonly'] = 'true'
          form.fields['sender_email'].initial = request.user.email
  
      if username:
          member = get_object_or_404(UserModel, username=username)
          recipients = [member.email, ]
          logger.debug('Recipients should be a single user: %s' % recipients)
  
      else:
          # site contact form.
          # Use first of settings.DEFAULT_CONTACTS or all superusers
          site_form = True
          member = None
          recipients = getattr(settings, "DEFAULT_CONTACTS", None)
          logger.debug('Recipients should be match DEFAULT_CONTACTS: %s' % recipients)
  
          if not recipients:
              recipients = UserModel.objects.filter(is_superuser=True).values_list('email', flat=True)
              warnings.warn(
                  "settings.DEFAULT_CONTACTS does not exist. You may want to create it.",
                  RuntimeWarning
              )
              logger.debug('Recipients should be superusers: %s' % recipients)
  
      if form.is_valid():
          if site_form:
              subject = "A {} contact form submission from {}".format(
                  site.name, form.cleaned_data['sender_name']
              )
          else:
              subject = "A message from {} on {}".format(form.cleaned_data['sender_name'], site.name)
          body = form.cleaned_data['body']
  
          sender_email = form.cleaned_data['sender_email']
  
          if 'send_a_copy' in request.POST:
              recipients.append(sender_email)
              logger.debug('Recipients should be match prior + sender email: %s' % recipients)
  
          mail = EmailMessage(
              subject=subject,
              body=body,
              from_email=sender_email,
              to=recipients
          )
          mail.send()
          return HttpResponseRedirect(success_url)
      return render(request, 'contact/simple_form.html', {
          'form': form,
          'site': site,
          'member': member
      })