make findBookedDays a static of schema

db/index.ts

@@ -20,22 +20,7 @@ function connect() {
 
 export async function getBookedDays() {
   await connect()
-
-  const bookings = await Booking.find(
-    {
-      status: { $in: [BOOKING_STATUS.REQUESTED, BOOKING_STATUS.CONFIRMED] },
-      $or: [
-        { endDate: { $gt: new Date() } },
-        { startDate: { $gt: new Date() } },
-      ],
-    },
-    'startDate endDate'
-  ).exec()
-
-  return bookings
-    .map((booking) => booking.days)
-    .flat()
-    .sort()
+  return Booking.findBookedDays()
 }
 
 export async function getBookingByUUID(uuid: string) {
@@ -62,10 +47,7 @@ export async function createBooking({
 
   if (booking.days.some((day: string) => bookedDays.includes(day))) {
     const error = new mongoose.Error.ValidationError(booking)
-    error.addError(
-      'endDate',
-      'At least on one day the van is not avaliable. Choose another startDate or endDate.'
-    )
+    error.addError('endDate', new mongoose.Error.ValidatorError())
     throw error
   }