Reconcile BigCommerce orders to FreshBooks invoices

**Objective:** For BigCommerce orders created from `{date-from}` to `{date-to}` (default: today), find the FreshBooks invoice that bills each one and report orders with no invoice and invoices whose amount or payment state disagrees.

**Step 1: Read the orders**

Call `bigcommerce-get-order` (bigcommerce server) with `date-created.from` set to `{date-from}` and `date-created.to` set to `{date-to}`. Keep `id`, `billing-email`, `total-including-tax`, `currency-code`, `payment-status` and `status`. Ignore orders whose `status` is cancelled or incomplete, and say how many you ignored.

**Step 2: Find the FreshBooks client**

For each distinct `billing-email`, call `freshbooks-get-client` (freshbooks server) with `email` set to it. Keep the client `id`. If there is no client, mark every order for that email as "no client".

**Step 3: Find the invoice**

Call `freshbooks-get-invoice` (freshbooks server) with `customer-id` set to the client `id` and `create-date.from` set to `{date-from}`. Match an invoice to an order, in this order of preference: `po-number` equal to the order `id`; otherwise the same `amount` as `total-including-tax` and the same `currency-code`. If two invoices match equally well, list both and do not pick one.

**Step 4: Compare**

For each matched pair compare `amount` with `total-including-tax`, and compare `payment-status` on the invoice with `payment-status` on the order. Flag differences. Allow a difference of `{tolerance}` (default 0.01) in amount.

**Step 5: Report**

A table of orders with: order id, email, order total, invoice number, invoice amount, order payment status, invoice payment status, and a verdict (matched, amount differs, payment state differs, no invoice, no client). Finish with counts per verdict.

**Rules & Guidelines:**

* `bigcommerce-get-order` is on the bigcommerce server. `freshbooks-get-client` and `freshbooks-get-invoice` are on the freshbooks server.
* Read-only. Never call `freshbooks-add-invoice`, `freshbooks-update-invoice`, `freshbooks-delete-invoice`, `freshbooks-add-payment` or any bigcommerce order write tool.
* Compare amounts only when both sides use the same currency; otherwise report the pair as "currency differs".

**Validation:**

* If no orders come back, say so and stop.
* If an order has no `billing-email`, report it as unmatchable rather than guessing.