Post Invoice

Create a new invoice.

Must reference a valid account via account_id.

Request Body (InvoiceRequest):

• invoice_num (required): Unique invoice number / identifier.
• invoice_type (default: "sales"): Values: sales, credit, refund, reimbursement.
• account_id (required): FK to the customer account.
• contact_id (optional): FK to the billing contact.
• stage (default: "draft"): Values: draft, open, paid, cancelled, void, uncollectible.
• description (optional): Invoice notes.
• total_amount (required): Final total.
• invoice_date (optional): Epoch timestamp.
• invoice_line_list (required): Array of line items, e.g. [{"description":"Widget","amount":99.99,"line_detail_dict":{"qty":1,"unit_price":99.99}}].

Response: The created invoice object.