Per-currency breakdown sorted by summed amount desc.
Currency of the scalar raised when single-currency. null
for empty windows or multi-currency windows.
Total number of donations counted across all currencies.
Scalar total when the window resolves to a single currency (either
because options.currency is set, or because only one currency
showed up in the WS stream). null when the window spans multiple
currencies — read byCurrency in that case.
Return shape of usePipelineDonationSum. Mirrors the
GET /schedules/campaigns/{id}/raisedREST response so overlay code can trivially combinebaseline + deltawithout shape juggling.