BREAKING_CHANGE: [vertexai] Make ChatSession and GenerativeModel final (#10569)

PiperOrigin-RevId: 617274754

Co-authored-by: Zhenyi Qi <zhenyiqi@google.com>

Author: copybara-service[bot]

java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/ChatSession.java

@@ -30,7 +30,7 @@
 import java.util.List;
 
 /** Represents a conversation between the user and the model */
-public class ChatSession {
+public final class ChatSession {
   private final GenerativeModel model;
   private List<Content> history = new ArrayList<>();
   private ResponseStream<GenerateContentResponse> currentResponseStream = null;

java-vertexai/google-cloud-vertexai/src/main/java/com/google/cloud/vertexai/generativeai/GenerativeModel.java

@@ -33,7 +33,7 @@
 import java.util.List;
 
 /** This class holds a generative model that can complete what you provided. */
-public class GenerativeModel {
+public final class GenerativeModel {
   private final String modelName;
   private final String resourceName;
   private final VertexAI vertexAi;