curl --request GET \
  --url https://openapi.pluuug.com/v1/contract/{contract_id}

{
  "id": 123,
  "contractNumber": "<string>",
  "title": "<string>",
  "amount": 123,
  "type": "I",
  "status": "P",
  "startDate": "2023-12-25",
  "endDate": "2023-12-25",
  "vatType": "E",
  "settlementFrequency": 1,
  "settlementCycle": "M",
  "settlementDay": 1,
  "inquiry": {
    "id": 123,
    "status": {
      "id": 123,
      "title": "<string>",
      "folder": {
        "id": 123,
        "name": "<string>"
      }
    },
    "name": "<string>",
    "estimate": "<string>",
    "inquiryDate": "2023-12-25"
  },
  "client": {
    "id": 123,
    "status": {
      "id": 123,
      "title": "<string>"
    },
    "companyName": "<string>",
    "inCharge": "<string>",
    "position": "<string>",
    "contact": "<string>",
    "email": "jsmith@example.com"
  },
  "categorySet": [
    {
      "id": 123,
      "title": "<string>"
    }
  ]
}