fix: double-booking on reserved slots

[saurabhraghuvanshii]

What does this PR do?

• Added reservedSlotUid parameter to booking flow to validate slot ownership

• Enhanced handleNewBooking to check for reserved slots before creating bookings

• Integrated slot reservation ID management into Booker store for consistent state

• Added automatic cleanup of reserved slots after successful booking creation

• Fixes [Bug] Booking flow allows double-booking reserved slots #23938

• Fixes CAL-6430

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Mandatory Tasks (DO NOT REMOVE)

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• 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.

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[github-actions]

This PR is being marked as stale due to inactivity.

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Walkthrough

This change threads a reserved slot identifier through the booking flow and enforces reservation checks. The Booker store adds slotReservationId with a setter. Hooks (useSlots, useHandleBookEvent) read from this store and pass the value as reservedSlotUid in booking inputs. The booking input schema and the booking-to-mutation mapper now include reservedSlotUid. handleNewBooking reads reservedSlotUid, performs pre-booking checks against reserved slots (ownership or availability) when not a dry run, and deletes the reserved slot after successful booking. useSlots/useHandleBookEvent variants under platform/features are aligned to source the ID from the Booker store.

Possibly related PRs

• chore: Log availability snapshot when booking is created #22782: Also modifies packages/features/bookings/lib/handleNewBooking.ts, touching booking creation flow and logging around availability.
• fix: ensure seated event reschedules send proper reschedule emails #22849: Also updates handleNewBooking.ts, altering reschedule-vs-schedule email logic within the same booking handler.
• refactor: handle emails and sms side effects #23578: Refactors notification side-effects in handleNewBooking.ts into BookingEmailSmsHandler, overlapping the same function/file.

Pre-merge checks and finishing touches

❌ Failed checks (2 warnings)

Check name	Status	Explanation	Resolution
Linked Issues Check	⚠️ Warning	The implementation correctly accepts and validates reservedSlotUid from the client and integrates it into handleNewBooking as required by issues #23938 and CAL-6430, but it does not perform the booking creation and reservation deletion within a single atomic transaction nor address reservation support for round-robin and collective events, and it lacks persistence of reservedSlotUid across sessions.	To satisfy the linked issues, modify handleNewBooking to wrap booking creation and reservation cleanup in one atomic database transaction so that cleanup failures rollback the booking, extend reserved-slot support to round-robin and collective event flows, and implement persistent storage (e.g., localStorage) of reservedSlotUid in the client.
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title Check	✅ Passed	The pull request title succinctly communicates the primary intent of the changeset which is to fix double-booking on reserved slots, and it accurately reflects the main issue addressed without extraneous detail.
Out of Scope Changes Check	✅ Passed	All modifications in this pull request are limited to implementing the reservedSlotUid parameter and its propagation through the Booker store, mutation input mapping, schema, handler, and hooks, with no unrelated or extraneous code changes introduced.
Description Check	✅ Passed	The pull request description clearly outlines the new reservedSlotUid parameter, enhancements to handleNewBooking, store integration, cleanup logic, and references the fixed issues, making it directly relevant to the changeset.

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[kart1ka]

Thank you for the PR. Can you please attach a loom video showing your fix works? We will also need test for this fix. Can you please add that as well?

[github-actions]

This PR is being marked as stale due to inactivity.

[supalarry]

Thank you for the contribution! I will be closing this PR though because it has been stale and another PR #24670 will adress this issue 🙏