test domo: add capabilities

src/rest/rest_devices_handlers.h

@@ -34,6 +34,9 @@
 #define kerror_body "{ \"status\": \"error\" }"
 #define kempty_body "{}"
 
+
+extern int capabilities_handler(restd_resp_t *response, void *arg);
+
 // Outlets
 extern int outlet_create_handler(restd_resp_t *response, void *arg);
 extern int outlet_list_handler(restd_resp_t *response, void *arg);