Scheduling some personal dates and managing participants

• ?show <last|next> -> Show last events, show next events
• ?add <id> -> Add yourself to a event
• ?remove <id> -> Remove yourself from a event
• ?newdate <DD.MM.YYYY - HH:MM>,<TEXT> -> Add a new event (maybe restricted access)
• ?deldate <id> -> Remove a event (maybe restricted access) ...

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