The new REST connector is a significant improvement over the old one, however I think the interface should be extended to specify a required / optional checkbox for each parameter (for a GET request), and the parameters should be automatically appended to the URL by the module / runtime instead of specifying via curly brackets.
The issue currently shows up when you have an optional rest parameter. Because the parameter name and '=' character are statically defined in the url, the request is made in this format => 'http://localhost:8080?foo='. Some servers / frameworks see this parameter as malformed. I think instead the parameter itself should be omitted (or an option can be set to omit null parameters). This would make integrations easier with e.g. ASPNET Core.