Issue: 3930, Fix MessageChatMemoryAdvisor to handle message updates correctly

[wilocu]

Summary

Fixes issue where MessageChatMemoryAdvisor incorrectly handles modified and resent messages by appending them as new messages
instead of replacing the original message and its response.

Fixes #3930

Problem

When a user modifies and resends an existing message, the current implementation:

• Keeps the old user message in memory
• Keeps the original AI response in memory
• Appends the new modified message
• Generates a new AI response

This leads to inconsistent conversation history with duplicate/conflicting information.

Solution

Enhanced MessageChatMemoryAdvisor and related components to:

• Track messages using unique identifiers (messageId in metadata)
• Detect when a message with the same ID already exists
• Remove the old message and its corresponding assistant response
• Add the new message, allowing a fresh AI response

Key Changes

• ChatMemoryRepository: Added findByMessageId() and deleteMessageAndResponse() default methods
• MessageWindowChatMemory: Added removeMessageAndResponse() method
• MessageChatMemoryAdvisor: Enhanced with message update detection and handling logic
• Tests: Added comprehensive test coverage for message update functionality

Backward Compatibility

✅ Fully backward compatible - existing functionality unchanged:

• Messages without explicit messageId work exactly as before
• Automatic ID generation based on content hash only affects true duplicates
• All existing tests pass without modification

Test Coverage

• Added testMessageUpdateFunctionality() - validates complete update workflow
• Added testMessageIdGeneration() - ensures consistent ID generation
• All existing tests continue to pass (8/8 in MessageChatMemoryAdvisorTests, 26/26 in ChatMemory tests)

Usage Example

// User sends initial message
UserMessage original = UserMessage.builder()
.text("What is the capital of France?")
.metadata(Map.of("messageId", "msg-001"))
.build();

// Later, user modifies and resends with same messageId
UserMessage updated = UserMessage.builder()
.text("What is the capital of Italy?")
.metadata(Map.of("messageId", "msg-001"))
.build();

// Result: Old message + response removed, new message added

Test Plan

• All existing unit tests pass
• New test cases cover message update scenarios
• Integration tests with MessageWindowChatMemory
• Memory management tests verify no regressions
• Java formatting and checkstyle validation pass

Signed-off-by: Mattia Pasetto [email protected]

I am still pretty new to contributions, please double check and let me know of any errors.