PairSuggestion: {
    key: string;
    percentOff: number;
    suggestAddon: string;
    text: string;
    variant: string;
}

"Add for % off" - the discount is on that add-on's first payment only. Never call it a bundle. Admin: a pairOffer experiment is unitType person, goal buy; every non-control variant's config is { whenAddon, suggestAddon, percentOff (5-90), text (<=120) } with the SAME whenAddon / suggestAddon (one pair per experiment); the server adds couponId.