Add Cancelled Text

[zangjiucheng]

This pull request introduces changes to the CalendarEvent class to include a new is_cancelled property and updates the related event reminder functionality and unit tests accordingly.

Enhancements to CalendarEvent class:

• Added a new is_cancelled boolean property to the CalendarEvent class to track the cancelled status of an event. (src/classes/CalendarEvent.ts) [1] [2] [3]
• Updated the CalendarEvent constructor and the fromGoogleCalendarEvent method to handle the is_cancelled property. (src/classes/CalendarEvent.ts) [1] [2]

Updates to event reminders:

• Modified the generateEventReminderChannelText function to check the is_cancelled property and adjust the reminder message accordingly. (src/utils/eventReminders.ts) [1] [2]

Unit tests:

• Added new test cases to verify the correct parsing and handling of cancelled events in the CalendarEvent class and related functions. (tests/unit/classes/CalendarEvent.test.ts, tests/unit/utils/googleCalendar.test.ts) [1] [2] [3] [4]## Description

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This change is