add extra_body to ChatCompletionRequest\CreateChatCompletionStream

[Novemberinp]

I need to add the extra_body field to the request body to support the activation or deactivation of deep thinking in the large model, as well as other parameters. Should we consider opening these parameters? I have learned that they are already supported in the CreateEmbeddings function. Should we consider fully enabling them, or should we add a custom body to meet this requirement?

[GYMmaorui]

+1