Add snooze support for calendar reminders (toast UI, service, DB) (#825)

* Filter reminder snooze options by default reminder

* Some updates.

* Fixing empty welcome page issue and attendee loading.

* Icon system for notifications and snooze options etc.

Wino.Core.Domain/Entities/Calendar/CalendarItem.cs

@@ -138,6 +138,7 @@ public class CalendarItem : ICalendarItem
     // TODO
     public string CustomEventColorHex { get; set; }
     public string HtmlLink { get; set; }
+    public DateTime? SnoozedUntil { get; set; }
     public CalendarItemStatus Status { get; set; }
     public CalendarItemVisibility Visibility { get; set; }