Extract duplicate AppointmentResponse construction to helper

- Created _to_appointment_response() helper function
- Replaced 5 duplicate AppointmentResponse constructions with helper calls
- Helper handles both explicit user_email and eager-loaded user relationship cases

backend/routes/booking.py

@@ -22,6 +22,30 @@ from shared_constants import SLOT_DURATION_MINUTES, MIN_ADVANCE_DAYS, MAX_ADVANC
 router = APIRouter(prefix="/api/booking", tags=["booking"])
 
 
+def _to_appointment_response(
+    appointment: Appointment,
+    user_email: str | None = None,
+) -> AppointmentResponse:
+    """Convert an Appointment model to AppointmentResponse schema.
+    
+    Args:
+        appointment: The appointment model instance
+        user_email: Optional user email. If not provided, uses appointment.user.email
+    """
+    email = user_email if user_email is not None else appointment.user.email
+    return AppointmentResponse(
+        id=appointment.id,
+        user_id=appointment.user_id,
+        user_email=email,
+        slot_start=appointment.slot_start,
+        slot_end=appointment.slot_end,
+        note=appointment.note,
+        status=appointment.status.value,
+        created_at=appointment.created_at,
+        cancelled_at=appointment.cancelled_at,
+    )
+
+
 def _get_bookable_date_range() -> tuple[date, date]:
     """Get the valid date range for booking (tomorrow to +30 days)."""
     today = date.today()
@@ -180,17 +204,7 @@ async def create_booking(
             detail="This slot has already been booked. Please select another slot.",
         )
     
-    return AppointmentResponse(
-        id=appointment.id,
-        user_id=appointment.user_id,
-        user_email=current_user.email,
-        slot_start=appointment.slot_start,
-        slot_end=appointment.slot_end,
-        note=appointment.note,
-        status=appointment.status.value,
-        created_at=appointment.created_at,
-        cancelled_at=appointment.cancelled_at,
-    )
+    return _to_appointment_response(appointment, current_user.email)
 
 
 # =============================================================================
@@ -214,17 +228,7 @@ async def get_my_appointments(
     appointments = result.scalars().all()
     
     return [
-        AppointmentResponse(
-            id=apt.id,
-            user_id=apt.user_id,
-            user_email=current_user.email,
-            slot_start=apt.slot_start,
-            slot_end=apt.slot_end,
-            note=apt.note,
-            status=apt.status.value,
-            created_at=apt.created_at,
-            cancelled_at=apt.cancelled_at,
-        )
+        _to_appointment_response(apt, current_user.email)
         for apt in appointments
     ]
 
@@ -270,17 +274,7 @@ async def cancel_my_appointment(
     await db.commit()
     await db.refresh(appointment)
     
-    return AppointmentResponse(
-        id=appointment.id,
-        user_id=appointment.user_id,
-        user_email=current_user.email,
-        slot_start=appointment.slot_start,
-        slot_end=appointment.slot_end,
-        note=appointment.note,
-        status=appointment.status.value,
-        created_at=appointment.created_at,
-        cancelled_at=appointment.cancelled_at,
-    )
+    return _to_appointment_response(appointment, current_user.email)
 
 
 # =============================================================================
@@ -315,17 +309,7 @@ async def get_all_appointments(
     
     # Build responses using the eager-loaded user relationship
     records = [
-        AppointmentResponse(
-            id=apt.id,
-            user_id=apt.user_id,
-            user_email=apt.user.email,  # Uses eager-loaded relationship
-            slot_start=apt.slot_start,
-            slot_end=apt.slot_end,
-            note=apt.note,
-            status=apt.status.value,
-            created_at=apt.created_at,
-            cancelled_at=apt.cancelled_at,
-        )
+        _to_appointment_response(apt)  # Uses eager-loaded relationship
         for apt in appointments
     ]
     
@@ -375,14 +359,4 @@ async def admin_cancel_appointment(
     await db.commit()
     await db.refresh(appointment)
     
-    return AppointmentResponse(
-        id=appointment.id,
-        user_id=appointment.user_id,
-        user_email=appointment.user.email,  # Uses eager-loaded relationship
-        slot_start=appointment.slot_start,
-        slot_end=appointment.slot_end,
-        note=appointment.note,
-        status=appointment.status.value,
-        created_at=appointment.created_at,
-        cancelled_at=appointment.cancelled_at,
-    )
+    return _to_appointment_response(appointment)  # Uses eager-loaded relationship