Support config-driven output formatting

src/helper/formatters/index.js

@@ -13,12 +13,14 @@
 const influxdbFormatter = require('./influxdbFormatter');
 const jsonFormatter = require('./jsonFormatter');
 const csvFormatter = require('./csvFormatter');
+const processFormatter = require('./processFormatter');
 
 // Built-in registry
 const registry = {
   influxdb: influxdbFormatter,
   json: jsonFormatter,
   csv: csvFormatter,
+  process: processFormatter,
 };
 
 /**

src/helper/formatters/processFormatter.js

@@ -0,0 +1,9 @@
+/**
+ * Process formatter
+ * Keeps the existing process-port behaviour: emit only changed fields as an object.
+ */
+function format(_measurement, metadata) {
+  return metadata.fields;
+}
+
+module.exports = { format };