Deleting imported gifts uses the configured identifiers

For GiveCampus constituent data and imports.

Use the deletion workflow's generated example/required headers, which derive from the active import configuration's unique fields. Matching can require gift identifiers and constituent identifiers together; do not assume a constituent-ID-only list or the original import CSV is sufficient. Review the deletion preview before approval. The service soft-deletes eligible imported gifts and related designation selections; it is not a refund of online payments. For failures, support needs the import configuration, deletion upload and exact error rather than repeated uploads with different filenames.