/**
 * Find the first league of each set and return pairs of
 * index to league name. Assumes that clubs are sorted by ascending league name.
 */
fun indexAgendaHeaders(agendaItems: List<ClubEntity>): List<Pair<Int, String>> {
    return agendaItems
        .mapIndexed { index, block -> index to block.clubLeague }
        .distinctBy { it.second }
}