curl --request POST \
  --url https://api.altostrat.io/v1/failover/{site_id}/gateways \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "interface": "ether1-wan"
}'

[
  {
    "gateway": "198.51.100.1",
    "is_dhcp": false
  }
]