fix: rollback booking status to CANCELLED on calendar sync failure

[sdip0971]

What this PR does
Fixes #28397
Fixes a state leak issue where a booking is permanently saved as ACCEPTED in the database even if EventManager.create fails to sync the event to the external calendar.

Previously, the backend would log the BookingCreatingMeetingFailed error but continue execution, returning a 200 OK to the frontend and resulting in a false "Success" UI state for the user.

How it works
This PR adds a synchronous compensation transaction inside RegularBookingService.ts. If the calendar integration fails:

It immediately executes a Prisma update to change the booking status to CANCELLED.

It sets a cancellationReason explicitly documenting the calendar integration failure.

It throws an HttpError(500) to halt backend execution. This forces the frontend's useMutation hook into its onError state, preventing the success redirect and ensuring the UI correctly displays the error toast.

Testing conditions (like isDryRun) are respected to ensure this doesn't break existing test suites.

[CLAassistant]

All committers have signed the CLA.

[cubic-dev-ai]

1 issue found across 1 file

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="packages/features/bookings/lib/service/RegularBookingService.ts">

<violation number="1" location="packages/features/bookings/lib/service/RegularBookingService.ts:2353">
P1: Booking cancellation is keyed to "all integrations failed" instead of calendar-sync failure, causing false cancellations and missed calendar-failure rollbacks.</violation>
</file>

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[sahitya-chandra]

Can you add the steps for how to reproduce this issue?

and video evidence of the issue

[sdip0971]

@sahitya-chandra Thanks for the review!

Steps to Reproduce:

1. Connect a Google Calendar to a user profile.
2. Force a calendar sync failure (e.g., manually corrupt the access token in the Credential table).
3. Attempt to book a meeting on the frontend.
4. Without this PR: The frontend incorrectly redirects to the green "Booking Confirmed" success page, even though the calendar API failed.
5. With this PR: The backend catches the specific calendar integration failure, rolls the DB status back to CANCELLED, and throws a 500 error to ensure the frontend displays the correct failure toast.

Here is the video evidence of the fix successfully catching the failure and updating the UI:

Screen.Recording.2026-03-18.at.8.54.16.PM.mov