Refactor ExtensionFilter to use simplified operation methods

Simplified the example by using the `getExtension()` method added in 4.1, along with the preexisting `addExtension()` method, rather than handling the map of extensions directly.

Author: ttelang

modules/ROOT/pages/chapter04/chapter04.adoc

@@ -855,8 +855,6 @@ package io.microprofile.tutorial.store.product.config;
 
 import org.eclipse.microprofile.openapi.models.Operation;
 import org.eclipse.microprofile.openapi.OASFilter;
-import java.util.LinkedHashMap;
-import java.util.Map;
 
 public class ExtensionFilter implements OASFilter {
     
@@ -867,49 +865,31 @@ public class ExtensionFilter implements OASFilter {
         }
         
         try {
-            // Get existing extensions (or create new map if null)
-            Map<String, Object> existingExtensions = operation.getExtensions();
-            if (existingExtensions == null) {
-                return operation; // No extensions to process
-            }
-            
-            // Create a new map with existing extensions
-            Map<String, Object> newExtensions = new LinkedHashMap<>(existingExtensions);
-            
             // Check if a custom timeout extension exists
-            if (newExtensions.containsKey("x-custom-timeout")) {
-                Object timeout = newExtensions.get("x-custom-timeout");
-                if (timeout != null) {
-                    int timeoutValue = Integer.parseInt(timeout.toString());
-                    if (timeoutValue > 30) {
-                        newExtensions.put("x-requires-approval", "true");
-                    }
+            Object timeout = operation.getExtension("x-custom-timeout");
+            if (timeout != null) {
+                int timeoutValue = Integer.parseInt(timeout.toString());
+                if (timeoutValue > 30) {
+                    operation.addExtension("x-requires-approval", "true");
                 }
             }
             
             // Check for rate limiting configuration
-            if (newExtensions.containsKey("x-rate-limit")) {
-                Object rateLimit = newExtensions.get("x-rate-limit");
-                if (rateLimit != null) {
-                    int rateLimitValue = Integer.parseInt(rateLimit.toString());
-                    if (rateLimitValue > 500) {
-                        newExtensions.put("x-high-volume", "true");
-                    }
+            Object rateLimit = operation.getExtension("x-rate-limit");
+            if (rateLimit != null) {
+                int rateLimitValue = Integer.parseInt(rateLimit.toString());
+                if (rateLimitValue > 500) {
+                    operation.addExtension("x-high-volume", "true");
                 }
             }
             
             // Check for authentication requirements
-            if (newExtensions.containsKey("x-requires-auth")) {
-                Object authLevel = newExtensions.get("x-requires-auth");
-                if (authLevel != null && "admin".equals(authLevel.toString())) {
-                    newExtensions.put("x-security-notice", 
-                        "This operation requires administrator privileges");
-                }
+            Object authLevel = operation.getExtension("x-requires-auth");
+            if (authLevel != null && "admin".equals(authLevel.toString())) {
+                operation.addExtension("x-security-notice", 
+                    "This operation requires administrator privileges");
             }
             
-            // Set the modified extensions map back
-            operation.setExtensions(newExtensions);
-            
         } catch (Exception e) {
             System.err.println("Error in ExtensionFilter: " + e.getMessage());
             e.printStackTrace();