1.26.0 upgrade: Add attributes to messages

[CakeCrusher]

depends on #18
example with file_search:

messages = client.beta.threads.messages.list(
    thread_id=thread.id
)

{
  "data": [
    {
      "id": "msg_ED5JAicrhN4hFz0tN3VL2nGy",
      "assistant_id": "asst_7Asu2r1ZCuz8FrydJUYKrGVY",
      "attachments": [],
      "completed_at": null,
      "content": [
        {
          "text": {
            "annotations": [
              {
                "end_index": 954,
                "file_citation": {
                  "file_id": "file-giEo3NN4k74QbUVOfP7TWOEK",
                  "quote": null
                },
                "start_index": 942,
                "text": "【4:0†source】",
                "type": "file_citation"
              }
            ],
            "value": "The parameters for creating an assistant using `openai_client.beta.assistants.create` include:\n\n- **instructions**: The system instructions that the assistant uses.\n- **name**: The name of the assistant.\n- **tools**: A list of tools enabled on the assistant, each entry specifying the tool type.\n- **model**: The model to be used by the assistant (e.g., \"gpt-4\").\n- **metadata**: A dictionary containing up to 16 key-value pairs that can be attached to the assistant.\n\nHere is an example of how these parameters might be used in a call to the `create` method:\n\n```python\nresponse = openai_client.beta.assistants.create(\n    instructions=\"You are an AI designed to provide examples.\",\n    name=\"Example Assistant\",\n    tools=[{\"type\": \"code_interpreter\"}],\n    model=\"gpt-4\",\n    metadata={\"str\": \"string\", \"int\": 1, \"bool\": True, \"list\": [1, 2, 3]},\n)\n```\n\nThis example assumes that the \"code_interpreter\" is an enabled tool for the assistant【4:0†source】."
          },
          "type": "text"
        }
      ],
      "created_at": 1715056757,
      "incomplete_at": null,
      "incomplete_details": null,
      "metadata": {},
      "object": "thread.message",
      "role": "assistant",
      "run_id": "run_uNgH6X3snV25MWy70BJswcCg",
      "status": null,
      "thread_id": "thread_UyFDMzEKDuKqVyoB02xMiuI4"
    },
    {
      "id": "msg_AfNLGo5pVMImBwX9NHZod7OF",
      "assistant_id": null,
      "attachments": [],
      "completed_at": null,
      "content": [
        {
          "text": {
            "annotations": [],
            "value": "what are the parameters to creating an assistant using openai_client.beta.assistants.create"
          },
          "type": "text"
        }
      ],
      "created_at": 1715056746,
      "incomplete_at": null,
      "incomplete_details": null,
      "metadata": {},
      "object": "thread.message",
      "role": "user",
      "run_id": null,
      "status": null,
      "thread_id": "thread_UyFDMzEKDuKqVyoB02xMiuI4"
    }
  ],
  "object": "list",
  "first_id": "msg_ED5JAicrhN4hFz0tN3VL2nGy",
  "last_id": "msg_AfNLGo5pVMImBwX9NHZod7OF",
  "has_more": false
}