curl --request POST \
  --url https://api.interchange.io/api/v2/storefront/storefronts/{storefrontId}/demand-signals/{signalId}/respond \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "payload": {
    "proposedCpm": 1,
    "currency": "<string>",
    "products": [
      {
        "productId": "<string>",
        "name": "<string>",
        "estimatedImpressions": 4503599627370495
      }
    ],
    "notes": "<string>"
  }
}
'

{
  "id": "<string>",
  "demandSignalId": "<string>",
  "demandSignalTargetId": "<string>",
  "sellerCustomerId": 0,
  "storefrontId": "<string>",
  "payload": {},
  "matchScore": 50,
  "actorUserId": 0,
  "createdAt": "<string>"
}