feat: send WhatsApp notification on sales invoice created

app/Notifications/Sales/InvoiceCreatedNotification.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace App\Notifications\Sales;
+
+use App\Models\SalesInvoice;
+use Illuminate\Bus\Queueable;
+use Illuminate\Contracts\Queue\ShouldQueue;
+use Illuminate\Notifications\Notification;
+use PromoSeven\UltraMessage\UltraMessageChannel;
+use PromoSeven\UltraMessage\UltraMessageMessage;
+
+class InvoiceCreatedNotification extends Notification implements ShouldQueue
+{
+    use Queueable;
+
+    public function __construct(private SalesInvoice $invoice) {}
+
+    public function via(mixed $notifiable): array
+    {
+        return [UltraMessageChannel::class];
+    }
+
+    public function toUltraMessage(mixed $notifiable): UltraMessageMessage
+    {
+        return UltraMessageMessage::text(
+            "Dear {$notifiable->name},\n\nInvoice *#{$this->invoice->invoice_number}* is ready.\n\nAmount Due: {$this->invoice->total_amount}\nDue Date: {$this->invoice->due_date}\n\nPlease arrange payment at your earliest convenience. Thank you."
+        );
+    }
+}