The Default System Prompt is not the first element in the messages array

[rafaelrddc]

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Bug description
When we use the chatClient class with "defaultSystem" and "MessageChatMemoryAdvisor", when making the call to OpenAI with a message history, the first element of the array is not of role "system"

Environment
Spring AI: 1.0.0-M5
Java version: 21.0.5-zulu

Steps to reproduce
I created a chatClient linked to a "defaultSystem" and with the "MessageChatMemoryAdvisor", and checked the order of the messages sent to OpenAI.

Expected behavior
The default system message will always be the first message in the array sent to OpenAI.

Minimal Complete Reproducible example
Please provide a failing test or a minimal complete verifiable example that reproduces the issue.
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[ThomasVitale]

Thanks for reporting this issue. I would recommend addressing this together with #873, making sure to implement a consistent and predictable strategy for placing system messages across different use cases.