curl --request POST \
  --url https://api.highwayapi.ai/v3/async/flux-2-flex \
  --header 'Authorization: <authorization>' \
  --header 'Content-Type: <content-type>' \
  --data '
{
  "seed": 123,
  "size": "<string>",
  "images": [
    {}
  ],
  "prompt": "<string>"
}
'

{
  "task_id": "<string>"
}