curl --request POST \
  --url https://api.example.com/api/import/preview \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "source": "<string>",
  "username": "<string>",
  "key": "<string>",
  "token": "<string>"
}
'

{
  "provider": "<string>",
  "source": "<string>",
  "total_files": 123,
  "total_bytes": 123,
  "extension_counts": {},
  "sample_files": [
    "<string>"
  ],
  "warnings": [
    "<string>"
  ]
}