SUCCESS! {
  id: '08c91506-11e9-11f1-b9bb-095ebc94b3c1',
  conversation_id: '2fe78a15-11e7-11f1-b9bb-095ebc94b3c1',
  sender_type: 'agent',
  sender_id: '05c4a90b-07d8-11f1-b9bb-095ebc94b3c1',
  message_text: 'Hello backend!',
  message_type: 'text',
  media_url: null,
  media_mime_type: null,
  media_caption: null,
  media_size_bytes: null,
  is_ai_generated: false,
  ai_model: null,
  ai_confidence: null,
  ai_prompt_tokens: null,
  ai_completion_tokens: null,
  ai_cost: null,
  status: 'sent',
  external_id: null,
  error_code: null,
  error_message: null,
  metadata: null,
  channel: null,
  sent_at: 2026-02-25T01:26:38.000Z,
  delivered_at: null,
  read_at: null,
  failed_at: null,
  created_at: 2026-02-25T01:26:38.000Z
}