Backend: Editing existing reservation

GitHub Issue: #191

Backend task for loading and updating a Vozni park reservation (GET and POST /drivepark/reservations/{reservationId}) – check the API spec and DB structure, reuse the lock and overlap check while ignoring the reservation's own booking, handle a vehicle change, implement, and verify against the spec.

Docs: Editing existing reservation Spec: GET /drivepark/reservations/{reservationId} (getDriveParkReservation), POST /drivepark/reservations/{reservationId} (updateDriveParkReservation), DriveParkReservationNewRequest, DriveParkReservation, DriveParkReservationNotFound, DriveParkReservationConflict in api-docs/openapi.yaml DB: DriveParkReservations, VehicleReservations in api/database/pending_schema.sql (-- DRIVE PARK --)

1. Double check API spec and DB structure

• The form has the same fields as Adding new reservation, prefilled. Check DriveParkReservation returns everything the form needs (vehicle id, brand, name and plate for the dropdown, dates, company, fullName, contact).
• Past reservations can be edited (docs). Check the spec has no “past” rule.
• Overlap check ignores the reservation’s own VehicleReservations row.
• Archived / deleted vehicle: checked only when vehicleId changes, so a past reservation of a since-archived vehicle can still be edited. Neispravno is always checked (period ending today or later).
• Vehicle change: both vehicles are locked, ascending Id. Check the lock order against the events/vehicles locking PR.
• Zapisnici: not linked to reservations; an update changes no record. Check nothing in the records reads reservation data.
• Labels: Figma CTA “PRIHVATI REZERVACIJU” and title “Uredi rezervaciju” are frontend only; the toast says the reservation was updated.
• Roles and permissions: drivepark.access on both endpoints.

2. Implementation

• Roles and permissions: require drivepark.access → 403.
• GET: load the reservation with its VehicleReservations row and vehicle → 200 DriveParkReservation; unknown id → 404.
• POST: in one transaction, lock the vehicle(s), run the shared availability and overlap helpers from Backend: Adding new reservation (excluding the own row), then update DriveParkReservations (UpdatedAt) and its VehicleReservations row (VehicleId, StartTime, EndTime).
• Validation → 400 validation_error, same as create.
• Response 200 with the updated DriveParkReservation.

3. Verify implementation against spec

• Routes, methods, request and response shapes match getDriveParkReservation and updateDriveParkReservation.
• 400 / 404 / 409 vehicle_unavailable / 409 vehicle_conflict can be produced; no undocumented ones.
• Moving a reservation by one day where it only overlaps itself → 200.
• Changing the vehicle to one booked on those days → 409; to a free one → 200, and the bar moves to the new row.
• Editing a past reservation of a vehicle that is now archived (same vehicle) → 200.
• BrandManager → 403.

Done when

A Manager of Vozni park can change any reservation, including past ones, without creating an overlap.