Set isBlocking true if the input type uses a handler that blocks.

src/main/java/io/sinistral/proteus/server/handlers/HandlerGenerator.java

@@ -466,6 +466,12 @@ else if (t.equals(HttpServerExchange.class) || t.equals(ServerRequest.class))
 
 			endpointInfo.setConsumes(consumesContentType);
 
+            //The handler for these two inputs types is blocking, so we set the flag
+            if (endpointInfo.getConsumes().equals("application/x-www-form-urlencoded")
+                    || endpointInfo.getConsumes().equals("multipart/form-data")) {
+                isBlocking = true;
+            }
+
 			endpointInfo.setPathTemplate(methodPath);
 
 			endpointInfo.setControllerMethod(m.getName());