docs: add javadoc on leader election exit flag

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/LeaderElectionManager.java

@@ -126,6 +126,7 @@ private void stopLeading() {
       // Note that some reconciliations might run for a very long time.
       System.exit(1);
     } else {
+      // just for testing purposes
       log.info("Stopped leading, configured not to exit");
     }
   }

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/LeaderElectionConfiguration.java

@@ -35,6 +35,8 @@ public class LeaderElectionConfiguration {
   private final Duration retryPeriod;
 
   private final LeaderCallbacks leaderCallbacks;
+
+  /** Set to false only for testing purposes. */
   private final boolean exitOnStopLeading;
 
   public LeaderElectionConfiguration(String leaseName, String leaseNamespace, String identity) {

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/config/LeaderElectionConfigurationBuilder.java

@@ -71,6 +71,7 @@ public LeaderElectionConfigurationBuilder withLeaderCallbacks(LeaderCallbacks le
     return this;
   }
 
+  /** Set to false only for testing purposes. */
   public LeaderElectionConfigurationBuilder withExitOnStopLeading(boolean exitOnStopLeading) {
     this.exitOnStopLeading = exitOnStopLeading;
     return this;