Constituents API updates are not an isolated identifier-only store

For GiveCampus integrations and API.

Constituents v2 maintains shared person/CRM data rather than an isolated identifier-to-email table. Creation uses the external identifier; updates target gc_constituent_id. Email entries include address, email_type and primary, with at most one primary address. Follow the documented full-update semantics rather than sending an ID-and-email-only PUT and assuming all other data survives. Manage ask amounts and designation personalization through their supported personalization workflow/import. API person changes can synchronize to VMS where enabled, so coordinate ownership of that shared data before bulk updates.