Output of reasoning_content that supports deepseek-r1 is required

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Expected Behavior
ChatModel.stream(xxx)
.flatMapSequential(f -> {
System.out.println(f.getResult().getOutput().getContent());
// Output reasoning_content
System.out.println(f.getResult().getOutput().getReasoningContent());
})

Current Behavior

ChatModel.stream(xxx)
.flatMapSequential(f -> {
// Output reasoning_content is not supported
System.out.println(f.getResult().getOutput().getContent());
})

Context

When launching LLM Q&A using ChatModel, the thinking response of deepseek-r1 will be output in reasoning_content. Currently, there is only content field in Message output. Unable to receive LLM's thinking, want to add related fields.

Start by tracing the ChatModel.stream API and the Message output object described in the examples. Then inspect how DeepSeek responses are represented and streamed, focusing on where content is currently exposed. Done means callers can receive reasoning_content alongside content when using deepseek-r1, with coverage for the streaming behavior.