feat(logging): enhance sampler result logging with response length

Signed-off-by: Johnny Hujol <itudoben@users.noreply.github.com>

Author: itudoben

src/main/java/io/github/delirius325/jmeter/backendlistener/elasticsearch/ElasticsearchBackendClient.java

@@ -245,8 +245,9 @@ public void handleSampleResults(List<SampleResult> results, BackendListenerConte
 
     for (SampleResult sr : results) {
       String respString = sr.getResponseDataAsString();
-      respString = respString.substring(0, Math.min(100, respString.length()));
-      logger.info("Handle sampler result {}: {}", sr.getSampleLabel(), respString);
+      int endIndex = Math.min(100, respString.length());
+      respString = respString.substring(0, endIndex);
+      logger.info("Handle sampler result ({}) {}: {}", endIndex, sr.getSampleLabel(), respString);
       ElasticSearchMetric metric = new ElasticSearchMetric(sr, context.getParameter(ES_TEST_MODE),
         context.getParameter(ES_TIMESTAMP), this.buildNumber,
         context.getBooleanParameter(ES_PARSE_REQ_HEADERS, false),