UX: no user feedback when adding existing signature

[ligi]

currently when you add an existing signature you press the submit button and nothing happens. This is confusing to users. Better would be SnackBar like thing similar to the success case - just with the extra info (already existed) instead of "Added"

[pipermerriam]

This would be the place to start if someone wants to work on this

ethereum-function-signature-registry/func_sig_registry/registry/views.py

Lines 85 to 97 in def6c03

	def post(self, *args, **kwargs):
	serializer = self.get_serializer(data=self.request.data)
	if not serializer.is_valid():
	return Response({'serializer': serializer})
	signature = serializer.save()
	messages.success(
	self.request._request,
	"Added signature '{0}' for function '{1}'".format(
	signature.bytes_signature.get_hex_display(),
	signature.text_signature,
	),
	)
	return redirect('signature-list')

[a5net]

I am rewriting this part now, so I will keep in mind this issue.