Optional registration link when creating event

[mmihalik]

closes #267

[rtrembecky]

@mmihalik create event za Webmastera s payloadom {"id":null,"year":2023,"school_year":"2023/2024","start":"2023-11-01T15:03:00.000Z","end":"2023-11-30T15:04:00.000Z","competition":0,"publication_set":[]} alebo {"id":null,"year":2023,"school_year":"2023/2024","start":"2023-11-03T15:08:00.000Z","end":"2023-11-24T15:08:00.000Z","competition":0} (rozdiel len v publication_set) stale hadze 500.

restoroval som db pred tym

[rtrembecky]

pri explicitnom passe registration_link: null: {"id":null,"year":2023,"school_year":"2023/2024","start":"2023-11-02T15:35:00.000Z","end":"2023-11-30T15:35:00.000Z","registration_link":null,"competition":0}

[mmihalik]

Už fachči podľa mňa