[feature] Option to create event directly hidden

Hi, It would be useful (for a user with an account) to create an event directly hidden that will not be shown in Gancio and that will not be published on the fediverse (only after it's made visible). Some users like to upload an uncompleted event and finish it later when they have all the information, so it's a bit unconvenient that it gets published by default when using a Gancio account. Thank you!