Allow Prometheus formatting to arbitrary Writer

implementations/micrometer-registry-prometheus/src/main/java/io/micrometer/prometheus/PrometheusMeterRegistry.java

@@ -76,14 +76,21 @@ private static List<String> tagValues(Meter.Id id) {
     public String scrape() {
         Writer writer = new StringWriter();
         try {
-            TextFormat.write004(writer, registry.metricFamilySamples());
+            scrape(writer);
         } catch (IOException e) {
             // This actually never happens since StringWriter::write() doesn't throw any IOException
             throw new RuntimeException(e);
         }
         return writer.toString();
     }
 
+    /**
+     * @param writer Target that serves the content to be scraped by Prometheus.
+     */
+    public void scrape(Writer writer) throws IOException {
+        TextFormat.write004(writer, registry.metricFamilySamples());
+    }
+
     @Override
     public Counter newCounter(Meter.Id id) {
         MicrometerCollector collector = collectorByName(id);