Enhance Neo4jChatMemoryRepository, expand integration tests, improve configuration, and update documentation

- Enhanced Neo4jChatMemoryRepository to correctly restore custom metadata for SystemMessage using SystemMessage.Builder.
- Refactored and clarified Neo4jChatMemoryRepository implementation code.
- Added comprehensive integration tests for Neo4jChatMemoryConfig and Neo4jChatMemoryRepository, including:
-- Index creation verification
-- Custom label support
-- Getter validation for all configuration properties
-- Tests for saving and retrieving SystemMessage metadata
-- Tests ensuring saveAll(conversationId, Collections.emptyList()) clears all messages and removes the conversation node
-- Tests for handling of messages with empty content and empty metadata
-- Improved overall test coverage for Neo4j persistence and configuration edge cases
- Fixed resource management bugs in test classes (ensured proper driver/session closure).
- Improved index creation logic in Neo4jChatMemoryConfig for reliability and logging.
- Updated documentation to include Neo4jChatMemoryRepository usage and configuration

Signed-off-by: enricorampazzo <enrico.rampazzo@live.com>
Signed-off-by: Mark Pollack <mark.pollack@broadcom.com>

spring-ai-docs/src/main/antora/modules/ROOT/pages/api/chat-memory.adoc

@@ -64,7 +64,7 @@ If you'd rather create the `InMemoryChatMemoryRepository` manually, you can do s
 ChatMemoryRepository repository = new InMemoryChatMemoryRepository();
 ----
 
-=== JDBC Repository
+=== JdbcChatMemoryRepository
 
 `JdbcChatMemoryRepository` is a built-in implementation that uses JDBC to store messages in a relational database. It is suitable for applications that require persistent storage of chat memory.
 
@@ -127,6 +127,7 @@ ChatMemory chatMemory = MessageWindowChatMemory.builder()
 | `spring.ai.chat.memory.repository.jdbc.initialize-schema` | Whether to initialize the schema on startup. | `true`
 |===
 
+
 ==== Schema Initialization
 
 The auto-configuration will automatically create the `ai_chat_memory` table using the JDBC driver. Currently, only PostgreSQL and MariaDB are supported.
@@ -135,6 +136,78 @@ You can disable the schema initialization by setting the property `spring.ai.cha
 
 If your project uses a tool like Flyway or Liquibase to manage your database schemas, you can disable the schema initialization and refer to link:https://github.com/spring-projects/spring-ai/tree/main/memory/spring-ai-model-chat-memory-jdbc/src/main/resources/org/springframework/ai/chat/memory/jdbc[these SQL scripts] for configuring those tools to create the `ai_chat_memory` table.
 
+=== Neo4j ChatMemoryRepository
+
+`Neo4jChatMemoryRepository` is a built-in implementation that uses Neo4j to store chat messages as nodes and relationships in a property graph database. It is suitable for applications that want to leverage Neo4j's graph capabilities for chat memory persistence.
+
+First, add the following dependency to your project:
+
+[tabs]
+======
+Maven::
++
+[source, xml]
+----
+<dependency>
+    <groupId>org.springframework.ai</groupId>
+    <artifactId>spring-ai-starter-model-chat-memory-neo4j</artifactId>
+</dependency>
+----
+
+Gradle::
++
+[source,groovy]
+----
+dependencies {
+    implementation 'org.springframework.ai:spring-ai-starter-model-chat-memory-neo4j'
+}
+----
+======
+
+Spring AI provides auto-configuration for the `Neo4jChatMemoryRepository`, which you can use directly in your application.
+
+[source,java]
+----
+@Autowired
+Neo4jChatMemoryRepository chatMemoryRepository;
+
+ChatMemory chatMemory = MessageWindowChatMemory.builder()
+    .chatMemoryRepository(chatMemoryRepository)
+    .maxMessages(10)
+    .build();
+----
+
+If you'd rather create the `Neo4jChatMemoryRepository` manually, you can do so by providing a Neo4j `Driver` instance:
+
+[source,java]
+----
+ChatMemoryRepository chatMemoryRepository = Neo4jChatMemoryRepository.builder()
+    .driver(driver)
+    .build();
+
+ChatMemory chatMemory = MessageWindowChatMemory.builder()
+    .chatMemoryRepository(chatMemoryRepository)
+    .maxMessages(10)
+    .build();
+----
+
+==== Configuration Properties
+
+[cols="2,5,1",stripes=even]
+|===
+|Property | Description | Default Value
+| `spring.ai.chat.memory.neo4j.sessionLabel` | The label for the nodes that store conversation sessions | `Session`
+| `spring.ai.chat.memory.neo4j.messageLabel` | The label for the nodes that store messages | `Message`
+| `spring.ai.chat.memory.neo4j.toolCallLabel` | The label for nodes that store tool calls (e.g. in Assistant Messages) | `ToolCall`
+| `spring.ai.chat.memory.neo4j.metadataLabel` | The label for nodes that store message metadata | `Metadata`
+| `spring.ai.chat.memory.neo4j.toolResponseLabel` | The label for the nodes that store tool responses | `ToolResponse`
+| `spring.ai.chat.memory.neo4j.mediaLabel` | The label for the nodes that store media associated with a message | `Media`
+|===
+
+==== Index Initialization
+
+The Neo4j repository will automatically ensure that indexes are created for conversation IDs and message indices to optimize performance. If you use custom labels, indexes will be created for those labels as well. No schema initialization is required, but you should ensure your Neo4j instance is accessible to your application.
+
 == Memory in Chat Client
 
 When using the ChatClient API, you can provide a `ChatMemory` implementation to maintain conversation context across multiple interactions.