You can use identify from the server to pass in traits for known IDs. These traits will only be tied to a browsing history when that user ID has been identified from the client using the JS API.
All Attribution server-side endpoints expect data in JSON format
A note on Auth headers
Attribution app uses a HTTP Auth for all server-side functions.
Your HTTPS request header should have a blank password and the username must be your "Project ID" from [Attribution app settings]https://dashboard.attributionapp.com/goto/settings/instructions)