V1

{
  "body": {

  },
  "headers": {
    "Accept": "application/json",
    "Content-Type": "application/json",
    "X-Merchant-Id": "{merchant-id}"
  },
  "method": "POST" <MODIFIED>,
  "path": "checkout-sessions/{checkout-session-id}/cancel/"
}

V2

{
  "body": {

  },
  "headers": {
    "Accept": "application/json",
    "Content-Type": "application/json",
    "X-Merchant-Id": "{merchant-id}"
  },
  "method": "PATCH" <MODIFIED>,
  "path": "checkout-sessions/{checkout-session-id}/cancel/"
}