curl --request POST \
  --url https://api.posta.co/letters/{id}/cancel \
  --header 'X-Api-Key: <api-key>'

import requests

url = "https://api.posta.co/letters/{id}/cancel"

headers = {"X-Api-Key": "<api-key>"}

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

print(response.text)

const options = {method: 'POST', headers: {'X-Api-Key': '<api-key>'}};

fetch('https://api.posta.co/letters/{id}/cancel', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "type": "<string>",
  "title": "<string>",
  "detail": "<string>",
  "status": 400,
  "errors": {}
}