Realize how to divide terms in the schedule

[eugrdn]

• schedule updates (numerator/denominator)
• test weeks, exams
• end of a semester

[eugrdn]

Each CRON sequence could be linked to an exact period of time. The problem was that current CRON library parser doesn't support year marker, that caused infinity repetition. Then it has been added manually in Sequence object:

type Sequence = {
    id: string;
    cron: Cron;
    year: number;
    numeratorStartsOn: number;
    room: string;
    lector: Email[];
    isPractice: boolean;
    type: EventWeekType;
    notes: Record<TDate, Note>;
};