List chat sessions

curl --request GET \
  --url https://api.open.cx/chat/sessions \
  --header 'Authorization: Bearer <token>'

{
  "items": [
    {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "status": "open",
      "channel": {
        "type": "web"
      },
      "contact": {
        "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
        "email": "jsmith@example.com",
        "phone_number": "<string>",
        "name": "<string>",
        "custom_data": {}
      },
      "language": "<string>",
      "assignee_id": "<string>",
      "handoff": {
        "sentiment": "angry",
        "summary": "<string>"
      },
      "created_at": "2023-11-07T05:31:56Z",
      "updated_at": "2023-11-07T05:31:56Z"
    }
  ],
  "next": "<string>"
}