See an invoice from payment to delivery in one timeline

**Objective:** For invoice `{invoice-number}`, show whether it was paid, shipped and delivered, in one timeline.

**Step 1: Find the invoice (FreshBooks server)**

Call `freshbooks-get-invoice` with invoice-number set to `{invoice-number}`. If more than one invoice matches, list them and stop. Note `id`, `customer-id`, `organization`, `po-number`, `amount`, `payment-status`, `date-paid` and `create-date`.

**Step 2: Find payments (FreshBooks server)**

Call `freshbooks-get-payment` with invoice-id set to the invoice id. List each payment date, type and amount.

**Step 3: Find the shipment (ShipStation server)**

Call `shipstation-get-shipment` with external-order-id set to the invoice-number; if nothing comes back, try the invoice's po-number. Take `shipment-id` and `shipment-number`.

**Step 4: Find label and delivery (ShipStation server)**

Call `shipstation-get-label` with shipment-id set to that shipment-id for `tracking-number`, `tracking-url`, `tracking-status`, `carrier-code` and `voided`. Then call `shipstation-get-fulfillment` with shipment-number set to the shipment-number for `delivered-at` and `carrier-name`.

**Step 5: Report**

A dated timeline: invoice created, each payment, shipped, delivered. Add a one-line status such as paid and delivered, paid but not shipped, or shipped but unpaid.

**Rules & Guidelines:**

* `freshbooks-get-invoice` and `freshbooks-get-payment` are on the freshbooks server; the shipment, label and fulfillment tools are on the shipstation server.
* Read-only. Do not call any freshbooks add, update, delete, mark or send tool.

**Validation:**

* If the invoice is not found, stop. If no shipment is found, report the invoice facts and say no shipment exists in ShipStation under that reference.
* If a label is voided, say so and use any non-voided label instead.