Count donors with several affiliations

For GiveCampus reporting.

For a prior-year affiliation count, choose the intended campaign/date range, include donors whose recorded affiliations contain the target affiliation even when other affiliations appear in the same export cell, then count distinct donors using the report's identity rules. Counting gift rows can count repeat donors more than once. Review joint and offline donor treatment before reconciling against public campaign totals. A rounded percentage cannot recover an exact donor count. Clarify fiscal versus calendar year.