curl --request PUT \
  --url https://api-sandbox.appcharge.com/components/v1/offer-design/{externalId} \
  --header 'Content-Type: application/json' \
  --header 'x-publisher-token: <api-key>' \
  --data '{
  "offerUiType": "SpecialOffer",
  "name": "Summer Special Edition",
  "externalId": "summer_special_offer",
  "backgroundImageUrl": "https://example.com/images/updated-summer-special.png",
  "title": {
    "text": "Hot New Deal",
    "fontColor": "#FFFF00",
    "fontSize": 18,
    "fontWeight": "bolder"
  }
}'

{
  "id": "507f1f77bcf86cd799439011",
  "offerUiType": "SpecialOffer",
  "name": "Summer Special",
  "externalId": "summer_special_offer",
  "backgroundImageUrl": "https://cdn.appcharge.com/507f1f77bcf86cd799439011_background.png",
  "title": {
    "text": "Limited Time Offer",
    "fontColor": "#FFFFFF",
    "fontSize": 16,
    "fontWeight": "bold"
  },
  "externalBackgroundImageUrl": "https://example.com/images/summer-special.png"
}