make findBookedDays a static of schema

db/booking.ts

@@ -64,6 +64,25 @@ BookingSchema.virtual('days').get(function () {
   return getDays({ startDate: this.startDate, endDate: this.endDate })
 })
 
+BookingSchema.static('findBookedDays', async function (): string[] {
+  console.log('in findBookedDays this is', this)
+  const bookings = await this.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) => booking.days)
+    .flat()
+    .sort()
+})
+
 const Model: mongoose.Model<Booking> =
   mongoose.models.Booking || mongoose.model('Booking', BookingSchema)