Narrows a registration feed by whether money changed hands.

all (the default) keeps the session-centric behaviour — every per-session registration the participant holds, including the free comp spots fanned out to a team's members for each league match. paidOnly returns just the registrations that requiredPayment (the activity-level "league registration" that covers the whole season, plus any individually-paid session drop-ins), so the captain's one season row surfaces instead of being drowned out by — or hidden behind — the per-match comps.