Know when a valuable customer unsubscribes from your emails

**Objective:** Find which people who unsubscribed from Mailchimp campaigns in the last `{lookback-days}` days (default 30) are Business Central customers, and rank them by what they buy. Use the Business Central company `{company}`; if it is empty, omit the `company` filter.

**Step 1: Recent unsubscribes**

Call `mailchimp-get-campaign-unsubscribe` with `unsubscribe-date.from` set to today minus the lookback. Keep email, first-name, last-name, company, campaign-name, unsubscribe-date and reason. Collapse duplicate emails to the latest unsubscribe.

**Step 2: Look each one up in Business Central**

For each email, call `business-central-get-customer` with `email` set to it. Keep customer-number, name, sales, balance, balance-due and salesperson-code. If there is no customer, call `business-central-get-contact` with `email` set to it and keep contact-number, company-name and salesperson-code.

**Step 3: Who owns the relationship**

For each distinct salesperson-code found, call `business-central-get-salesperson` with `salesperson-code` set to it to get the salesperson's name and email.

**Step 4: Report**

Table 1, customers: email, customer name, sales, balance-due, campaign-name, reason, salesperson name and email, sorted by sales highest first. Table 2, contacts who are not customers. Then one line counting unsubscribes with no match in Business Central.

**Rules & Guidelines:**

* `mailchimp-get-campaign-unsubscribe` is on the mailchimp server. `business-central-get-customer`, `business-central-get-contact` and `business-central-get-salesperson` are on the business-central server.
* This prompt is read-only. Never resubscribe anyone: do NOT call `mailchimp-update-list-member` or `mailchimp-add-list-member`, and do NOT call `business-central-update-customer` or `business-central-update-contact`.

**Validation:**

* If there are no unsubscribes in the window, say so and stop.
* Match emails case-insensitively after trimming spaces.
* An unsubscribe reason may be empty; show it as blank rather than guessing one.