chore: Enable javadoc in the default profile (#525)

Any javadoc errors (not warnings) will make
Maven fail

This fixes #524

---------

Signed-off-by: Jeff Mesnil <[email protected]>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: jmesnil

pom.xml

@@ -454,6 +454,10 @@
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
             </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-javadoc-plugin</artifactId>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-surefire-plugin</artifactId>
@@ -516,10 +520,6 @@
                         <groupId>org.apache.maven.plugins</groupId>
                         <artifactId>maven-source-plugin</artifactId>
                     </plugin>
-                    <plugin>
-                        <groupId>org.apache.maven.plugins</groupId>
-                        <artifactId>maven-javadoc-plugin</artifactId>
-                    </plugin>
                     <plugin>
                         <groupId>org.apache.maven.plugins</groupId>
                         <artifactId>maven-gpg-plugin</artifactId>

spec/src/main/java/io/a2a/json/JsonUtil.java

@@ -79,7 +79,7 @@ private static GsonBuilder createBaseGsonBuilder() {
      * <p>
      * Used throughout the SDK for consistent JSON serialization and deserialization.
      *
-     * @see GsonFactory#createGson()
+     * @see GsonBuilder
      */
     public static final Gson OBJECT_MAPPER = createBaseGsonBuilder()
             .registerTypeHierarchyAdapter(Part.class, new PartTypeAdapter())

spec/src/main/java/io/a2a/util/Utils.java

@@ -1,5 +1,6 @@
 package io.a2a.util;
 
+import java.lang.reflect.Type;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -43,7 +44,7 @@ public class Utils {
     /**
      * Deserializes JSON string into a typed object using Gson.
      * <p>
-     * This method uses the pre-configured {@link #OBJECT_MAPPER} to parse JSON.
+     * This method uses the pre-configured {@link JsonUtil#fromJson(String, Class)} to parse JSON.
      *
      * @param <T> the target type
      * @param data JSON string to deserialize