curl --request PUT \
  --url https://api.awfixer.app/v2/destination-calendars \
  --header 'Authorization: <authorization>' \
  --header 'Content-Type: application/json' \
  --data '{
  "integration": "apple_calendar",
  "externalId": "https://caldav.icloud.com/26962146906/calendars/1644422A-1945-4438-BBC0-4F0Q23A57R7S/",
  "delegationCredentialId": "<string>"
}'

{
  "status": "success",
  "data": {
    "userId": 123,
    "integration": "<string>",
    "externalId": "<string>",
    "credentialId": 123
  }
}