InvoiceBranding

{
    "logo_url": "https://customer.example/logo.png",
    "letterhead_pdf_url": "https://customer.example/letterhead.pdf",
    "letterhead_pdf_base64": "string",
    "letterhead_margins": {
        "top": 45,
        "right": 20,
        "bottom": 30,
        "left": 20
    }
}