List a customer unit's aliases by its key

Lists the aliases that land signals on this unit, without naming its customer. The key is looked up across the organization ignoring letter case. When more than one unit carries it in another letter case (legacy duplicates across customers, or case variants on one customer), the exact spelling decides; when that does not single one out either, the answer is 409 CUSTOMER_UNIT_AMBIGUOUS: use the customer’s unit routes, where the key is exact.