further work on billing

db/booking.ts

@@ -1,6 +1,7 @@
 import * as mongoose from 'mongoose'
 import { v4 as uuidv4 } from 'uuid'
 import { dateFormatBackend, getDays } from '../helpers/date'
+import { BillDocument } from './bill'
 import { BookerDocument } from './booker'
 import { BOOKING_STATUS } from './enums'
 
@@ -9,6 +10,7 @@ export interface BookingDocument
     mongoose.SchemaTimestampsConfig {
   uuid: string
   booker: BookerDocument
+  bill: BillDocument
   startDate: Date
   endDate: Date
   status: BOOKING_STATUS
@@ -35,6 +37,11 @@ const BookingSchema = new mongoose.Schema<BookingDocument>(
       ref: 'Booker',
       required: true,
     },
+    bill: {
+      type: mongoose.Schema.Types.ObjectId,
+      ref: 'Bill',
+      required: false,
+    },
     startDate: {
       type: Date,
       required: true,
@@ -56,11 +63,6 @@ const BookingSchema = new mongoose.Schema<BookingDocument>(
     purpose: { type: String, required: false },
     org: { type: String, required: false },
     destination: { type: String, required: false },
-    bill: {
-      type: mongoose.Schema.Types.ObjectId,
-      ref: 'bill',
-      required: false,
-    },
   },
   {
     timestamps: true,