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/sales/pax/pax.component.ts

@@ -1,5 +1,5 @@
 import { Component, Inject, OnInit } from '@angular/core';
-import { UntypedFormBuilder, UntypedFormGroup } from '@angular/forms';
+import { FormControl, FormGroup } from '@angular/forms';
 import { MAT_DIALOG_DATA, MatDialogRef } from '@angular/material/dialog';
 
 @Component({
@@ -8,16 +8,17 @@ import { MAT_DIALOG_DATA, MatDialogRef } from '@angular/material/dialog';
   styleUrls: ['./pax.component.css'],
 })
 export class PaxComponent implements OnInit {
-  form: UntypedFormGroup;
+  form: FormGroup<{
+    pax: FormControl<number>;
+  }>;
 
   constructor(
     public dialogRef: MatDialogRef<PaxComponent>,
     @Inject(MAT_DIALOG_DATA) public data: number,
-    private fb: UntypedFormBuilder,
   ) {
     // Create form
-    this.form = this.fb.group({
-      pax: '',
+    this.form = new FormGroup({
+      pax: new FormControl<number>(0, { nonNullable: true }),
     });
   }
 
@@ -28,7 +29,7 @@ export class PaxComponent implements OnInit {
   }
 
   accept(): void {
-    const pax = +this.form.value.pax;
+    const pax = this.form.value.pax ?? 0;
     this.dialogRef.close(pax);
   }
 }