curl --request POST \
  --url https://api.olostep.com/v1/files \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "filename": "<string>",
  "purpose": "context"
}
'

{
  "id": "<string>",
  "object": "<string>",
  "created": 123,
  "upload_url": "<string>",
  "expires_in": 123
}