curl --request POST \
  --url https://b.anny.co/api/v1/items \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/vnd.api+json' \
  --data '
{
  "data": {
    "type": "<string>",
    "attributes": {
      "quantity": "<string>",
      "single_gross_amount": "<string>",
      "tax_rate": "<string>",
      "currency": "<string>",
      "title": "<string>",
      "gross_amount": "<string>"
    },
    "relationships": {
      "document": {
        "data": {
          "type": "<string>",
          "id": "<string>"
        }
      },
      "product": {
        "data": {
          "type": "<string>",
          "id": "<string>"
        }
      }
    },
    "meta": {}
  }
}
'

import requests

url = "https://b.anny.co/api/v1/items"

payload = { "data": {
        "type": "<string>",
        "attributes": {
            "quantity": "<string>",
            "single_gross_amount": "<string>",
            "tax_rate": "<string>",
            "currency": "<string>",
            "title": "<string>",
            "gross_amount": "<string>"
        },
        "relationships": {
            "document": { "data": {
                    "type": "<string>",
                    "id": "<string>"
                } },
            "product": { "data": {
                    "type": "<string>",
                    "id": "<string>"
                } }
        },
        "meta": {}
    } }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/vnd.api+json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/vnd.api+json'},
  body: JSON.stringify({
    data: {
      type: '<string>',
      attributes: {
        quantity: '<string>',
        single_gross_amount: '<string>',
        tax_rate: '<string>',
        currency: '<string>',
        title: '<string>',
        gross_amount: '<string>'
      },
      relationships: {
        document: {data: {type: '<string>', id: '<string>'}},
        product: {data: {type: '<string>', id: '<string>'}}
      },
      meta: {}
    }
  })
};

fetch('https://b.anny.co/api/v1/items', 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://b.anny.co/api/v1/items",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'data' => [
        'type' => '<string>',
        'attributes' => [
                'quantity' => '<string>',
                'single_gross_amount' => '<string>',
                'tax_rate' => '<string>',
                'currency' => '<string>',
                'title' => '<string>',
                'gross_amount' => '<string>'
        ],
        'relationships' => [
                'document' => [
                                'data' => [
                                                                'type' => '<string>',
                                                                'id' => '<string>'
                                ]
                ],
                'product' => [
                                'data' => [
                                                                'type' => '<string>',
                                                                'id' => '<string>'
                                ]
                ]
        ],
        'meta' => [
                
        ]
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/vnd.api+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://b.anny.co/api/v1/items"

	payload := strings.NewReader("{\n  \"data\": {\n    \"type\": \"<string>\",\n    \"attributes\": {\n      \"quantity\": \"<string>\",\n      \"single_gross_amount\": \"<string>\",\n      \"tax_rate\": \"<string>\",\n      \"currency\": \"<string>\",\n      \"title\": \"<string>\",\n      \"gross_amount\": \"<string>\"\n    },\n    \"relationships\": {\n      \"document\": {\n        \"data\": {\n          \"type\": \"<string>\",\n          \"id\": \"<string>\"\n        }\n      },\n      \"product\": {\n        \"data\": {\n          \"type\": \"<string>\",\n          \"id\": \"<string>\"\n        }\n      }\n    },\n    \"meta\": {}\n  }\n}")

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

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

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

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

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://b.anny.co/api/v1/items")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/vnd.api+json")
  .body("{\n  \"data\": {\n    \"type\": \"<string>\",\n    \"attributes\": {\n      \"quantity\": \"<string>\",\n      \"single_gross_amount\": \"<string>\",\n      \"tax_rate\": \"<string>\",\n      \"currency\": \"<string>\",\n      \"title\": \"<string>\",\n      \"gross_amount\": \"<string>\"\n    },\n    \"relationships\": {\n      \"document\": {\n        \"data\": {\n          \"type\": \"<string>\",\n          \"id\": \"<string>\"\n        }\n      },\n      \"product\": {\n        \"data\": {\n          \"type\": \"<string>\",\n          \"id\": \"<string>\"\n        }\n      }\n    },\n    \"meta\": {}\n  }\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://b.anny.co/api/v1/items")

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

request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/vnd.api+json'
request.body = "{\n  \"data\": {\n    \"type\": \"<string>\",\n    \"attributes\": {\n      \"quantity\": \"<string>\",\n      \"single_gross_amount\": \"<string>\",\n      \"tax_rate\": \"<string>\",\n      \"currency\": \"<string>\",\n      \"title\": \"<string>\",\n      \"gross_amount\": \"<string>\"\n    },\n    \"relationships\": {\n      \"document\": {\n        \"data\": {\n          \"type\": \"<string>\",\n          \"id\": \"<string>\"\n        }\n      },\n      \"product\": {\n        \"data\": {\n          \"type\": \"<string>\",\n          \"id\": \"<string>\"\n        }\n      }\n    },\n    \"meta\": {}\n  }\n}"

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

{
  "data": {
    "id": "<string>",
    "type": "items",
    "attributes": {
      "name": "<string>",
      "quantity": 123,
      "unit_price": 123,
      "total": 123,
      "tax_rate": 123,
      "tax_amount": 123,
      "currency": "<string>"
    },
    "links": {
      "self": "<string>"
    },
    "relationships": {
      "invoice": {
        "data": {
          "type": "<string>",
          "id": "<string>"
        },
        "links": {
          "self": "<string>"
        }
      },
      "itemable": {
        "data": {
          "type": "<string>",
          "id": "<string>"
        },
        "links": {
          "self": "<string>"
        }
      }
    }
  }
}