What does this PR do?

• Fixes #21050 /claim #21050

Video Demo

This demo shows - on creation of an event in outlook calendar the CalendarCache is updated through the webhook Cron job was triggered manually through api - http://localhost:3000/api/calendar-cache/cron?apiKey=

https://www.loom.com/share/468bf851a93d49849b2dab27fe751efd?sid=458f9244-e4fe-4632-897d-b93835535ff6

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• I have updated the developer docs in /docs if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

Summary by mrge

Added caching and webhook support for Outlook (Office365) calendar availability to improve performance and enable real-time updates.

• New Features
  • Implemented webhook endpoint to receive Outlook calendar change notifications and refresh cache.
  • Added cache layer for Outlook calendar availability queries.
  • Updated database schema to store Outlook subscription info.