Fix README new ChatClient migration snippet

Author: tzolov

README.md

@@ -14,7 +14,7 @@ On our march to release 1.0.0 M1 we have made several breaking changes.  Apologi
 
 **(22.05.2024)**
 
-A major change was made that took the 'old' `ChatClient` and moved the functionality into `ChatModel`.  The 'new' `ChatClient` now takes an instance of `ChatModel`. This was done do support a fluent API for creating and executing prompts in a style similar to other client classes in the Spring ecosystem, such as `RestClient`, `WebClient`, and `JdbcClient`.  Refer to the [JavaDoc](https://docs.spring.io/spring-ai/docs/1.0.0-SNAPSHOT/api/) for more information on the Fluent API, proper reference documentation is coming shortly. 
+A major change was made that took the 'old' `ChatClient` and moved the functionality into `ChatModel`.  The 'new' `ChatClient` now takes an instance of `ChatModel`. This was done do support a fluent API for creating and executing prompts in a style similar to other client classes in the Spring ecosystem, such as `RestClient`, `WebClient`, and `JdbcClient`.  Refer to the [JavaDoc](https://docs.spring.io/spring-ai/docs/1.0.0-SNAPSHOT/api/) for more information on the Fluent API, proper reference documentation is coming shortly.
 
 We renamed the 'old' `ModelClient` to `Model` and renamed implementing classes, for example `ImageClient` was renamed to `ImageModel`.  The `Model` implementation represent the portability layer that converts between the Spring AI API and the underlying AI Model API.
 
@@ -25,39 +25,39 @@ NOTE: The `ChatClient` class is now in the package `org.springframework.ai.chat.
 #### Approach 1
 
 Now, instead of getting an Autoconfigured `ChatClient` instance, you will get a `ChatModel` instance.  The `call` method signatures after renaming remain the same.
-To adapt your code should refactor you code to change use of the type `ChatClient` to `ChatModel` 
+To adapt your code should refactor you code to change use of the type `ChatClient` to `ChatModel`
 Here is an example of existing code before the change
 
 ```java
 @RestController
-public class OldSimpleAiController { 
-    
+public class OldSimpleAiController {
+
     private final ChatClient chatClient;
-    
+
     public OldSimpleAiController(ChatClient chatClient) {
         this.chatClient = chatClient;
     }
-    
-    @GetMapping("/ai/simple") 
+
+    @GetMapping("/ai/simple")
     Map<String, String> completion(@RequestParam(value = "message", defaultValue = "Tell me a joke") String message) {
         return Map.of("generation", chatClient.call(message));
     }
 }
 ```
 
-Now after the changes this will be 
+Now after the changes this will be
 
 ```java
 @RestController
 public class SimpleAiController {
-    
+
     private final ChatModel chatModel;
-    
+
     public SimpleAiController(ChatModel chatModel) {
         this.chatModel = chatModel;
     }
-    
-    @GetMapping("/ai/simple") 
+
+    @GetMapping("/ai/simple")
     Map<String, String> completion(@RequestParam(value = "message", defaultValue = "Tell me a joke") String message) {
         return Map.of("generation", chatModel.call(message));
     }
@@ -80,9 +80,9 @@ Here is an example of existing code before the change
 ```java
 @RestController
 class OldSimpleAiController {
-    
+
     ChatClient chatClient;
-    
+
     OldSimpleAiController(ChatClient chatClient) {
         this.chatClient = chatClient;
 	}
@@ -97,23 +97,22 @@ class OldSimpleAiController {
 }
 ```
 
-
 Now after the changes this will be
 
 ```java
 @RestController
 class SimpleAiController {
 
-    private final ChatClient.Builder builder;
-    
+    private final ChatClient chatClient;
+
     SimpleAiController(ChatClient.Builder builder) {
-      this.builder = builder;
+      this.builder = builder.build();
     }
-    
-    @GetMapping("/ai/simple") 
+
+    @GetMapping("/ai/simple")
     Map<String, String> completion(@RequestParam(value = "message", defaultValue = "Tell me a joke") String message) {
         return Map.of(
-                "generation", 
+                "generation",
                 chatClient.prompt().user(message).call().content()
         );
     }
@@ -130,7 +129,7 @@ There is a tag in the GitHub repository called [v1.0.0-SNAPSHOT-before-chatclien
 ```bash
 git checkout tags/v1.0.0-SNAPSHOT-before-chatclient-changes
 
-./mvnw clean install -DskipTests  
+./mvnw clean install -DskipTests
 ```