Add product keys

curl --request POST \
  --url https://api.fungies.io/v0/offers/{offerId}/keys/add \
  --header 'Content-Type: application/json' \
  --header 'x-fngs-public-key: <api-key>' \
  --header 'x-fngs-secret-key: <api-key>' \
  --data '{
  "productId": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
  "productKeys": [
    "<string>"
  ],
  "fileName": "<string>"
}'

{
  "status": "<string>",
  "data": {
    "success": true
  }
}