Reconcile Chargebee invoices to Dynamics GP receivables

**Objective:** For the customer `{customer-id}` compare Chargebee invoices with Dynamics GP receivables between `{date-from}` and `{date-to}` (default: the last 90 days). Use `{gp-company}` as the GP company when given.

**Step 1: Chargebee invoices**

Call `chargebee-get-invoice` (chargebee server) with `customer-id`, `date.from` and `date.to`. Keep id, date, total, amount-paid, amount-due, status, po-number and currency-code.

**Step 2: GP receivables**

Call `dynamics-gp-get-rm-trx` (dynamics-gp server) with `customer-id` (the same value; if nothing is returned, resolve the GP customer number with `dynamics-gp-get-rm-customer` using the customer name), `document-date.from` and `document-date.to`.

**Step 3: Match**

Match each Chargebee invoice to a GP transaction by `po-number` equal to `customer-po-number`, then by the Chargebee invoice id appearing in `document-number` or `document-description`, then by equal total against `document-amount` on a nearby date. Never match one GP transaction to two invoices.

**Step 4: Report**

Three lists: matched invoices with any amount difference, Chargebee invoices missing from GP, and GP invoice-type transactions with no Chargebee invoice. End with totals for each system and the net difference.

**Rules & Guidelines:**

* `chargebee-get-invoice` is on the chargebee server; `dynamics-gp-get-rm-trx` and `dynamics-gp-get-rm-customer` are on the dynamics-gp server.
* Read only. Do not call `dynamics-gp-rm-trx-add` or any other write tool.
* Ignore GP transactions whose void-status marks them voided, but count them separately.

**Validation:**

* If either side returns nothing, say which and stop after reporting the other side.
* If currencies differ, do not compare amounts; list the invoices unmatched by amount.