curl --request GET \
  --url https://api.withflex.com/v1/files/{id} \
  --header 'Authorization: Bearer <token>'

{
  "file": {
    "file_id": "<string>",
    "purpose": "account_requirement",
    "size": 123,
    "created_at": "<string>",
    "filename": "<string>",
    "type": "<string>",
    "expires_at": "<string>"
  }
}