curl --request POST \
  --url https://api.example.com/conversations/{conversationId}/messages \
  --header 'Content-Type: application/json' \
  --data '
{
  "content": "<string>",
  "metadata": {}
}
'

{
  "userMessage": {
    "id": "<string>",
    "conversationId": "<string>",
    "role": "USER",
    "content": "<string>",
    "createdAt": "<string>",
    "model": "<string>",
    "aiOperationId": "<string>",
    "hasFeedback": true,
    "inputTokens": 123,
    "outputTokens": 123,
    "processingTimeMs": 123,
    "source": "<string>"
  },
  "assistantMessage": {
    "id": "<string>",
    "conversationId": "<string>",
    "role": "USER",
    "content": "<string>",
    "createdAt": "<string>",
    "model": "<string>",
    "aiOperationId": "<string>",
    "hasFeedback": true,
    "inputTokens": 123,
    "outputTokens": 123,
    "processingTimeMs": 123,
    "source": "<string>"
  }
}