Feature: Tax Regimes are added so that different bills with different series can be printed for Different regimes such as VAT and GST

Chore: Model relationships updated to make them simpler
Chore: Bill printing majorly refactored for it

Due to the sheer depth of the changes. There can be showstoppers. Please test it carefully

bookie/src/app/guest-book/guest-book-list/guest-book-list.component.ts

@@ -1,5 +1,5 @@
 import { Component, OnInit } from '@angular/core';
-import { UntypedFormBuilder, UntypedFormControl, UntypedFormGroup } from '@angular/forms';
+import { FormControl, FormGroup } from '@angular/forms';
 import { MatDialog } from '@angular/material/dialog';
 import { ActivatedRoute, Router } from '@angular/router';
 import * as moment from 'moment';
@@ -22,27 +22,29 @@ import { GuestBookListDataSource } from './guest-book-list-datasource';
 export class GuestBookListComponent implements OnInit {
   data: BehaviorSubject<GuestBook[]> = new BehaviorSubject<GuestBook[]>([]);
   dataSource: GuestBookListDataSource = new GuestBookListDataSource(this.data);
-  form: UntypedFormGroup;
+  form: FormGroup<{
+    date: FormControl<Date>;
+  }>;
+
   /** Columns displayed in the table. Columns IDs can be added, removed, or reordered. */
   displayedColumns = ['sno', 'name', 'phone', 'pax', 'date', 'action'];
 
   constructor(
     private route: ActivatedRoute,
     private router: Router,
-    private fb: UntypedFormBuilder,
     private dialog: MatDialog,
     private toaster: ToasterService,
     private ser: GuestBookService,
   ) {
     // Create form
-    this.form = this.fb.group({
-      date: '',
+    this.form = new FormGroup({
+      date: new FormControl(new Date(), { nonNullable: true }),
     });
     this.listenToDateChange();
   }
 
   listenToDateChange(): void {
-    (this.form.get('date') as UntypedFormControl).valueChanges
+    this.form.controls.date.valueChanges
       .pipe(map((x) => moment(x).format('DD-MMM-YYYY')))
       .subscribe((x) =>
         this.ser.list(x).subscribe((list: GuestBookList) => {