curl --request PUT \
  --url https://{base_url_domain}/api/global/v1/shipping/retailers/{id}/merchant-settings/{setting_id} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "merchant": {
    "code": "acme_inc",
    "name": "ACME Inc.",
    "custom_fields": {
      "is_gift": {
        "value": true
      },
      "order_details": {
        "value": "test details"
      },
      "department": {
        "id": 3,
        "label": "Shipping"
      },
      "priority_levels": [
        {
          "id": 1,
          "label": "Urgent"
        },
        {
          "id": 2,
          "label": "High"
        }
      ],
      "cost_of_goods": {
        "amount": 156.99,
        "currency": "USD"
      },
      "assigned_user": {
        "value": 42
      }
    }
  },
  "default_tpb_group_id": 5,
  "default_duties_tpb_group_id": 5
}
'

import requests

url = "https://{base_url_domain}/api/global/v1/shipping/retailers/{id}/merchant-settings/{setting_id}"

payload = {
    "merchant": {
        "code": "acme_inc",
        "name": "ACME Inc.",
        "custom_fields": {
            "is_gift": { "value": True },
            "order_details": { "value": "test details" },
            "department": {
                "id": 3,
                "label": "Shipping"
            },
            "priority_levels": [
                {
                    "id": 1,
                    "label": "Urgent"
                },
                {
                    "id": 2,
                    "label": "High"
                }
            ],
            "cost_of_goods": {
                "amount": 156.99,
                "currency": "USD"
            },
            "assigned_user": { "value": 42 }
        }
    },
    "default_tpb_group_id": 5,
    "default_duties_tpb_group_id": 5
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.put(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'PUT',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    merchant: {
      code: 'acme_inc',
      name: 'ACME Inc.',
      custom_fields: {
        is_gift: {value: true},
        order_details: {value: 'test details'},
        department: {id: 3, label: 'Shipping'},
        priority_levels: [{id: 1, label: 'Urgent'}, {id: 2, label: 'High'}],
        cost_of_goods: {amount: 156.99, currency: 'USD'},
        assigned_user: {value: 42}
      }
    },
    default_tpb_group_id: 5,
    default_duties_tpb_group_id: 5
  })
};

fetch('https://{base_url_domain}/api/global/v1/shipping/retailers/{id}/merchant-settings/{setting_id}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://{base_url_domain}/api/global/v1/shipping/retailers/{id}/merchant-settings/{setting_id}",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "PUT",
  CURLOPT_POSTFIELDS => json_encode([
    'merchant' => [
        'code' => 'acme_inc',
        'name' => 'ACME Inc.',
        'custom_fields' => [
                'is_gift' => [
                                'value' => true
                ],
                'order_details' => [
                                'value' => 'test details'
                ],
                'department' => [
                                'id' => 3,
                                'label' => 'Shipping'
                ],
                'priority_levels' => [
                                [
                                                                'id' => 1,
                                                                'label' => 'Urgent'
                                ],
                                [
                                                                'id' => 2,
                                                                'label' => 'High'
                                ]
                ],
                'cost_of_goods' => [
                                'amount' => 156.99,
                                'currency' => 'USD'
                ],
                'assigned_user' => [
                                'value' => 42
                ]
        ]
    ],
    'default_tpb_group_id' => 5,
    'default_duties_tpb_group_id' => 5
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://{base_url_domain}/api/global/v1/shipping/retailers/{id}/merchant-settings/{setting_id}"

	payload := strings.NewReader("{\n  \"merchant\": {\n    \"code\": \"acme_inc\",\n    \"name\": \"ACME Inc.\",\n    \"custom_fields\": {\n      \"is_gift\": {\n        \"value\": true\n      },\n      \"order_details\": {\n        \"value\": \"test details\"\n      },\n      \"department\": {\n        \"id\": 3,\n        \"label\": \"Shipping\"\n      },\n      \"priority_levels\": [\n        {\n          \"id\": 1,\n          \"label\": \"Urgent\"\n        },\n        {\n          \"id\": 2,\n          \"label\": \"High\"\n        }\n      ],\n      \"cost_of_goods\": {\n        \"amount\": 156.99,\n        \"currency\": \"USD\"\n      },\n      \"assigned_user\": {\n        \"value\": 42\n      }\n    }\n  },\n  \"default_tpb_group_id\": 5,\n  \"default_duties_tpb_group_id\": 5\n}")

	req, _ := http.NewRequest("PUT", url, payload)

	req.Header.Add("Authorization", "Bearer <token>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.put("https://{base_url_domain}/api/global/v1/shipping/retailers/{id}/merchant-settings/{setting_id}")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"merchant\": {\n    \"code\": \"acme_inc\",\n    \"name\": \"ACME Inc.\",\n    \"custom_fields\": {\n      \"is_gift\": {\n        \"value\": true\n      },\n      \"order_details\": {\n        \"value\": \"test details\"\n      },\n      \"department\": {\n        \"id\": 3,\n        \"label\": \"Shipping\"\n      },\n      \"priority_levels\": [\n        {\n          \"id\": 1,\n          \"label\": \"Urgent\"\n        },\n        {\n          \"id\": 2,\n          \"label\": \"High\"\n        }\n      ],\n      \"cost_of_goods\": {\n        \"amount\": 156.99,\n        \"currency\": \"USD\"\n      },\n      \"assigned_user\": {\n        \"value\": 42\n      }\n    }\n  },\n  \"default_tpb_group_id\": 5,\n  \"default_duties_tpb_group_id\": 5\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://{base_url_domain}/api/global/v1/shipping/retailers/{id}/merchant-settings/{setting_id}")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Put.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"merchant\": {\n    \"code\": \"acme_inc\",\n    \"name\": \"ACME Inc.\",\n    \"custom_fields\": {\n      \"is_gift\": {\n        \"value\": true\n      },\n      \"order_details\": {\n        \"value\": \"test details\"\n      },\n      \"department\": {\n        \"id\": 3,\n        \"label\": \"Shipping\"\n      },\n      \"priority_levels\": [\n        {\n          \"id\": 1,\n          \"label\": \"Urgent\"\n        },\n        {\n          \"id\": 2,\n          \"label\": \"High\"\n        }\n      ],\n      \"cost_of_goods\": {\n        \"amount\": 156.99,\n        \"currency\": \"USD\"\n      },\n      \"assigned_user\": {\n        \"value\": 42\n      }\n    }\n  },\n  \"default_tpb_group_id\": 5,\n  \"default_duties_tpb_group_id\": 5\n}"

response = http.request(request)
puts response.read_body

{
  "errors": [
    {
      "type": "parameters",
      "message": "The supplied parameters are invalid.",
      "details": [
        {
          "key": "hold_until_date",
          "message": "The date must be in the future."
        }
      ]
    }
  ]
}

{
  "errors": [
    {
      "type": "not_found",
      "message": "The server could not find the requested resource."
    }
  ]
}

{
  "errors": [
    {
      "type": "unable_to_process",
      "message": "The supplied parameters are invalid.",
      "details": [
        {
          "key": "hold_until_date",
          "message": "The date must be in the future."
        }
      ]
    }
  ]
}