Explore ways to signal to form administrators when a mailing address is unaltered or "verified" [AddressComplete]

## Description

An address might be considered "verified" if the form filler hasn't altered the input after Canada Post API lookup.

Consider whether this is something we want to track with the form response to indicate to form administrators when a mailing address is indeed matching one that is "validated" in the Canada Post DB.

Otherwise, the functionality might be considered as providing value as a "gloried" auto-complete.

How might we do so without adding unecessary noise to "raw" response data?

Start by tracing the AddressComplete Canada Post API lookup and how the form response represents raw address data. Define an agreed signal for an unaltered or verified address without adding unnecessary raw-response noise; done requires a documented decision on the response shape and its administrator-facing meaning.

Written by the indexing model from the issue text.