add: response macros

add: preparation for more macro endpoints

src/endpoint.c

@@ -84,8 +84,5 @@ endpoint_response_json(endpoint_response_t *response, int status_code, const cJS
         }
     }
 
-    LOGGER_ERR("failed to print schedule json\n");
-
-    static const char content[] = "failed to print json";
-    endpoint_response_text(response, status_code, content, STRLEN(content));
+    M_RESPONSE_TEXT_STATIC(LOGGER_ERR, response, 500, "failed to print json");
 }