Shared email and multiple constituent IDs

For GiveCampus constituent data and imports.

The email-based identifier assignment collects all matching external IDs from the applicable source records, deduplicates/sorts them, and stores them separated by semicolons. It cannot infer which spouse made the gift from a shared email address alone. There is no demonstrated report switch that reliably selects the actual donor automatically. Resolve ambiguous identity using the source records and supported matching process; do not simply choose the first ID.