[$50] Don't delete connected calendars, just flag as deleted

[maxceem]

Branch feature/interview-update.

We have endpoint to delete connected calendars which was implemented in this challenge https://www.topcoder.com/challenges/af9a1041-7a78-484d-87d3-5aec9e87b578?tab=details

• DELETE /taas/user-meeting-settings/:userId/calendars/:calendarId
• Instead of actually deleting calendars we should keep them, and just mark them as deleted, like with flag isDeleted: true. (We need to keep calendars because maybe we have some interview scheduled with calendar we are deleting, so better we have access token to that calendar in case we need to make any change for already scheduled meeting).
• When we get UserMeetingSettings using endpoint GET /taas/user-meeting-settings/:userId we should NOT return calendars marked as deleted.
• When we connect a new calendar and there is existent deleted calendar with the same id we have to update its details and mark it as not deleted isDeleted: false. So there should be never duplicate calendars with the same id even if it was deleted. When we connect already deleted calendar this might mean that we re-connect previously deleted calendar. I'm not sure if this situation would really happen or Nylas would alway give a new id but better support it.
• Make sure that we don't have any of the issues which we have in this issue [$75] Missing fields of connected calendars #590

@maxceem, when we delete a calendar in the previous flow, we didn't used to delete it from Nylas server, but we deleted from the UserMeetingSettings.nylasCalendars record. So Nylas won't give a new id.

[maxceem]

@mahidulalvi-bonic paid via https://www.topcoder.com/challenges/d0ed9ed1-7758-4629-b36b-49409caf850e

[sandhiyakavi]

Verified in Dev Env. The id is same for the account deleted and added again.

[sdgun]

Unable to verify this in production since we haven't released connect calender feature to production yet.