curl --request POST \
  --url https://api.proxyscrape.com/v4/account/{subAccountId}/serp-api/subuser/{subUserId}/update \
  --header 'Content-Type: application/json' \
  --header 'api-token: <api-key>' \
  --data '
{
  "username": "<string>",
  "password": "<string>"
}
'

{
  "id": "<string>",
  "username": "<string>",
  "created_at": "<string>"
}