Add new webhook instance

curl --request POST \
  --url https://api.chift.eu/webhooks \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "event": "<string>",
  "url": "<string>",
  "signingsecret": "<string>",
  "integrationid": 123
}'

{
  "webhookid": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "accountid": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "createdby": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "createdon": "2023-11-07T05:31:56Z",
  "event": "<string>",
  "url": "<string>",
  "status": "active",
  "integrationid": 123
}