curl -L -X POST 'https://flux.postacksolutions.com/api/contacts/add' \
  -H 'Authorization: Bearer YOUR_ACCESS_TOKEN' \
  -H 'Content-Type: application/json' \
  -d '{
    "contactUserId": "6EAJHS27:user_456"
  }'

{
  "success": true,
  "contactId": "uuid-here"
}