Know which overdue customers email can still reach

**Objective:** List the Intacct customers with invoices more than `{days-overdue}` days overdue (default 30) and an open balance of at least `{min-amount-due}` (default 0.01), and show whether Drip can still reach each of them by email.

**Step 1: Find overdue invoices in Intacct**

Call `intacct-get-invoice` with `due-date.to` set to today minus the days overdue and `total-due.min` set to the minimum amount due. Group the results by customer-id: invoice count, sum of total-due, oldest due-date. If nothing comes back, say there are no overdue invoices at that threshold and stop.

**Step 2: Collect each customer's email addresses**

For each customer, call `intacct-get-customer` with `customer-id` and keep its email and status. Then call `intacct-get-contact` with `company-name` set to the customer-name and keep every non-blank email. Compare emails case-insensitively and drop duplicates.

**Step 3: Check each email in Drip**

For each email, call `drip-get-subscriber` with `email` set to it. Classify the customer:

* Reachable: at least one email is a Drip subscriber whose status is active.
* Unsubscribed: every email found in Drip is unsubscribed.
* Not in Drip: emails exist in Intacct but none is a Drip subscriber.
* No email on file: Intacct holds no email for the customer or its contacts.

**Step 4: Report**

A table sorted by overdue total, largest first: customer-name, customer-id, overdue total, overdue invoices, oldest due-date, best email (an active one if any), reachability, Drip tags. Then a count of customers and overdue total per reachability class.

**Rules & Guidelines:**

* `intacct-get-invoice`, `intacct-get-customer` and `intacct-get-contact` are on the intacct server. `drip-get-subscriber` is on the drip server.
* This prompt is read-only. Do not call `drip-add-subscriber-tag`, `drip-add-subscriber`, `drip-add-subscriber-to-campaign`, `drip-start-subscriber-workflow`, `drip-update-subscriber`, `intacct-update-customer` or any other write tool on either server. If the user wants these customers tagged in Drip, point them to the tag-overdue-customers prompt.

**Validation:**

* Compare Drip status values case-insensitively.
* Never suggest re-subscribing an unsubscribed person. Say collections for that customer must go through another channel.
* If invoices carry different transaction-currency values, total them per currency rather than adding them together.