Keep the HubSpot product library in step with BigCommerce

**Objective:** Make the HubSpot product library match up to `{max-records}` BigCommerce products (default 25, optionally only names containing `{product-name}`), matched by SKU. Nothing is written until the user confirms.

**Step 1: Read products from BigCommerce**

Call `bigcommerce-get-product` with `name.contains` set to `{product-name}` if given and `max-records` set to `{max-records}` (25 if empty). Keep `id`, `sku`, `name`, `price`, `cost-price`, `type` and `visible`. Products with an empty `sku` cannot be matched: list them and leave them out. Variant SKUs are not synced.

**Step 2: Compare with the HubSpot product library**

The join is the BigCommerce `sku` against the HubSpot `sku`, compared exactly after trimming. For each product, call `hubspot-get-products` with `sku` set to it.

* No match: call `hubspot-get-products` with `name` set to the BigCommerce `name`. If that finds a product, list it as a possible match with a different SKU and leave it alone. Otherwise the product goes on the create list.
* One match: compare `name`, `unit-price` and `unit-cost`. Any difference puts the product on the update list with the before and after values.
* More than one match: list the duplicates and leave them alone.

**Step 3: Confirm**

Show products to create (name, SKU, price, cost, type), products to update (record-id, field, current value, new value) and products skipped with the reason. Ask for an explicit yes and offer to exclude rows. Do not continue without a yes.

**Step 4: Write and verify**

For each confirmed new product, call `hubspot-add-product` once with `name`, `sku`, `price` from the BigCommerce `price`, `cost` from `cost-price` when it is above zero, and `product-type` set to inventory for a physical product or non_inventory for a digital one. For each confirmed change, call `hubspot-update-product` once with `id` set to the HubSpot `record-id` and only the fields that differ. Then call `hubspot-get-products` with `sku` set to each SKU and confirm the values. Report created, updated, failed and skipped rows.

**Rules & Guidelines:**

* `bigcommerce-get-product` is on the bigcommerce server; `hubspot-get-products`, `hubspot-add-product` and `hubspot-update-product` are on the hubspot server.
* The only write tools allowed are `hubspot-add-product`, once per confirmed new product, and `hubspot-update-product`, once per confirmed change, both only after the confirmation in Step 3. Call no other hubspot-add, hubspot-update, hubspot-rename, hubspot-remove, hubspot-subscribe, hubspot-unsubscribe or hubspot-import tool.
* Never call `bigcommerce-product-add`, `bigcommerce-product-update`, `bigcommerce-product-delete`, `bigcommerce-product-metafield-add` or any other bigcommerce add, update or delete tool. BigCommerce is only read here.
* Copy the regular `price`, not `sale-price`; a sale is temporary. Do not set `billing-frequency` or `owner-id`.

**Validation:**

* If `bigcommerce-get-product` returns nothing, say so and stop.
* If the user declines or does not answer, stop with nothing written.
* If a product does not show the new values on re-read, say so and do not retry blindly.