/claim https://github.com/calcom/cal.com/issues/9485

Summary

This PR fixes the CalDAV integration issue with Fastmail (and other CalDAV servers) causing duplicate and erroneous invitation emails.

Changes

Added SCHEDULE-AGENT=CLIENT to ATTENDEE properties in both createEvent and updateEvent methods.

What this fixes:

1. Duplicate invitations - CalDAV servers (Fastmail, etc.) were sending their own invitation emails in addition to Cal.com’s emails
2. Spec compliance - Per RFC 6638 Section 7.1, SCHEDULE-AGENT=CLIENT tells the CalDAV server that the client is responsible for handling invitations

Technical Details

Modified packages/lib/CalendarService.ts:

• Line 171-179: Add SCHEDULE-AGENT=CLIENT in createEvent()
• Line 259-266: Add SCHEDULE-AGENT=CLIENT in updateEvent()
• Line 195 & 277: Use modified iCalString with the new property

The fix modifies the iCal string after generation to add SCHEDULE-AGENT=CLIENT; to all ATTENDEE entries, preventing the CalDAV server from sending duplicate invitation emails.

Testing

Tested with:

• Event creation via CalDAV
• Event updates via CalDAV
• Verified iCal output contains SCHEDULE-AGENT=CLIENT on ATTENDEE lines

Fixes #9485

Ready for review!