Interface Challenge

interface Challenge {
    id: number;
    type: "regular" | "onboarding" | "group";
    title: string;
    header: string;
    start_date_time: string;
    end_date_time: string;
    cover_image: string;
    cover_thumbnail: null | string;
    instructions: null | ChallengeContent;
    results: ChallengeContent[];
    observation_count: number;
    species_count: number;
    challenge_user: null | ChallengeUser;
    targets: ChallengeTarget[];
    group: null | { id: number; name: string };
}