JdbcChatMemoryRepository do not persist Media in UserMessage

Expected Behavior
When using JdbcChatMemoryRepository it is expected that you will be able to continue a chat conversation keeping all the information that the User passed to the LLM model such as the text and also the Media resources (i.e.: for multimodal vision capable LLM models).

Current Behavior
JdbcChatMemoryRepository, as it is designed in version 1.0.0, persists only the following information:

• conversation_id (not an intrinsic field of the Message, passed in the saveAll method to group the messages pertaining to a given conversation)
• content (the text part of the message)
• type (the message type as a string representation of the Enum org.springframework.ai.chat.messages.MessageType)
• timestamp (a database generated field, for ordered retrieval purpose)

This behaviour lack a way to persist the Media attached to a UserMessage.

Context
With the use of JdbcChatMemoryRepository the LLM lose the capability to continue the conversation about a previously attached Media.

InMemoryChatMemory does not have any issues about keeping the Media attached to the Chat History.

I understand that the ChatMemory is not to be intended as a strategy to persist a Chat History but keeping Media attached to the UserMessage for the purpose of continuing a conversation about a given context (Media included) should be the standard behaviour of every ChatMemory implementation.

The only workaround I found is to write a custom implementation of ChatMemoryRepository capable to persist and retrieve the chat memory (at least for the UserMessage and AssistantMessage message types) serializing the content of the Media field if present.

Start with the JdbcChatMemoryRepository entry point and inspect how UserMessage content, type, and timestamp are persisted and reconstructed. Trace the database representation used for chat memory and determine how attached Media is handled during save and retrieval. Done means a resumed conversation preserves UserMessage Media as well as text, with coverage for the affected message flow.