Update keep-alive doc

Author: sebastianlorenzo88

docs/guide/protocols/http/keepAlive.md

@@ -1,9 +1,10 @@
 #### Keep alive
 
-Jmeter-java-dsl maintains a persistent http connection for subsequent requests to the same server.
-It is done by sending `Connection: keep-alive` header.
-If you want to disable keep-alive logic and force a server to close connection after each request then use`.useKeepAlive(false)` in a given `httpSampler` or `httpDefaults`.
+By default, **JMeter Java DSL** uses a persistent HTTP connection (sending the `Connection: keep-alive` header) to reuse the same socket for multiple requests to the same server.
 
+To force server to close the connection after each request, you can disable keep-alive with `.useKeepAlive(false)` either on an individual `httpSampler` or globally on `httpDefaults`.
+
+This can be useful when you’re load-testing an API that enforces a strict limit on the number of simultaneous sockets per client. If you leave keep-alive enabled, each virtual user will hold its socket open for the duration of the test, consuming the gateway’s connection pool.
 
 ```java
 import static us.abstracta.jmeter.javadsl.JmeterDsl.*;
@@ -14,10 +15,13 @@ public class PerformanceTest {
   public void test1() throws Exception {
     testPlan(
         threadGroup(1, 10,
+            //Disable keep-alive for this sampler: sends Connection: close header and close the connection after this request
             httpSampler("https://myservice1.com")
-                .useKeepAlive(false), 
+                .useKeepAlive(false),
+            // Explicitly enable keep-alive for this sampler: sends Connection: keep-alive header and keeps the connection open
             httpSampler("https://myservice2.com")
                 .useKeepAlive(true),
+            //No keep-alive configuration, so it will use the default keep-alive behavior (keep-alive enabled)
             httpSampler("https://myservice3.com")
         )
     ).run();
@@ -26,11 +30,16 @@ public class PerformanceTest {
   @Test
   public void test2() throws Exception {      
     testPlan(
+        //Disable keep-alive globally for all samplers in this test plan
         httpDefaults()
             .useKeepAlive(false), 
         threadGroup(1, 10,
+            // These samplers inherit keep-alive disabled from httpDefaults()
             httpSampler("https://myservice1.com"),
-            httpSampler("https://myservice2.com")
+            httpSampler("https://myservice2.com"),
+            // Explicitly enable keep-alive for this sampler overriding the global setting
+            httpSampler("https://myservice3.com")
+                .useKeepAlive(true)
        )
     ).run();
   }

jmeter-java-dsl/src/main/java/us/abstracta/jmeter/javadsl/http/DslHttpDefaults.java

@@ -192,6 +192,8 @@ public DslHttpDefaults followRedirects(boolean enable) {
 
   /**
    * Specifies if by default HTTP connection should be kept alive.
+   * <p>
+   * This can be overwritten by {@link DslHttpSampler#useKeepAlive(boolean)}.
    *
    * @param enable sets either to enable or disable persistent connection
    * @return the config element for further configuration or usage.