API sync can overwrite manual designation names

For GiveCampus integrations and API.

Designation PUT updates find a school designation by its GiveCampus ID and write the supplied name, description and external identifier. A sync that stores or discovers an existing GC ID can overwrite manual name changes; manual creation does not permanently protect them. POST creation is not an automatic upsert by name/external ID. Group membership uses a separate group API, so an absent grouping field in a designation update is not itself a group-removal instruction. Inspect the actual version/payload and explicit group reconciliation behavior; do not generalize blank/omitted semantics across all endpoints. In v2 visible:false also triggers removal from campaigns.