Enable stacktraces and causal chain of causes. Add a couple of tests to validate stacktrace and cause are included in responses (#6315)

spring-boot-libraries/src/main/java/com/baeldung/boot/problem/advice/ExceptionHandler.java

@@ -5,5 +5,12 @@ import org.zalando.problem.spring.web.advice.ProblemHandling;
 
 @ControllerAdvice
 public class ExceptionHandler implements ProblemHandling {
+    
+    // The causal chain of causes is disabled by default, 
+    // but we can easily enable it by overriding the behavior:
+    @Override
+    public boolean isCausalChainsEnabled() {
+        return true;
+    }
 
 }

spring-boot-libraries/src/main/java/com/baeldung/boot/problem/configuration/ProblemDemoConfiguration.java

@@ -12,6 +12,8 @@ public class ProblemDemoConfiguration {
 
     @Bean
     public ObjectMapper objectMapper() {
-        return new ObjectMapper().registerModules(new ProblemModule(), new ConstraintViolationProblemModule());
+        // In this example, stack traces support is enabled by default. 
+        // If you want to disable stack traces just use new ProblemModule() instead of new ProblemModule().withStackTraces()
+        return new ObjectMapper().registerModules(new ProblemModule().withStackTraces(), new ConstraintViolationProblemModule());
     }
 }