I've been trying all day to work out the generation of the deviceId, via Postman. Your instructions are:
Authenticate yourself with an fortniteIOSGameClient token with your preferred method of authentication.
Call https://account-public-service-prod.ol.epicgames.com/account/api/public/account/{accountId}/deviceAuth with method POST. Your response should look something like:
{
"deviceId": "...",
"accountId": "...",
"secret": "...",
"userAgent": "Any HTTP Client/0.1",
}
So "Authenticate yourself with an fortniteIOSGameClient" - I go to the table later in the document and pull out:
Client Name Client ID Secret
fortniteIOSGameClient 3446cd72694c4a4485d81b77adbb2141 9209d4a5e25a457fb9b07489d313b41a
I then reuse the client ID in the URL for the deviceAuth (X below), and use the generated OAuth token as a bearer token in the authentication of the second request: