Add wallet balance to User model and implement Atoll/Island management

- Added `wallet_balance` field to the User model.
- Updated UserAdmin to include `wallet_balance` in the admin interface.
- Created serializers and views for Atoll and Island management.
- Implemented endpoints for listing, creating, and updating Atolls and Islands.
- Enhanced payment processing with UUIDs for Payment and Topup models.
- Added migration files for new fields and constraints.
- Improved error handling and validation in various views.
- Updated email templates for better responsiveness and SEO.

billing/models.py

@@ -1,35 +1,37 @@
 from django.db import models
 from django.utils import timezone
 from api.models import User
+import uuid
 
 # Create your models here.
 
 from devices.models import Device
+
 # Create your models here.
 
+
 class Payment(models.Model):
     PAYMENT_TYPES = [
-        ('WALLET', 'Wallet'),
-        ('TRANSFER', 'Transfer'),
+        ("WALLET", "Wallet"),
+        ("TRANSFER", "Transfer"),
     ]
-
-    id = models.CharField(primary_key=True, max_length=255)
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
     number_of_months = models.IntegerField()
     amount = models.FloatField()
     paid = models.BooleanField(default=False)
-    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='payments')
+    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="payments")
     paid_at = models.DateTimeField(null=True, blank=True)
-    method = models.CharField(max_length=255, choices=PAYMENT_TYPES, default='TRANSFER')
+    method = models.CharField(max_length=255, choices=PAYMENT_TYPES, default="TRANSFER")
     expires_at = models.DateTimeField(null=True, blank=True)
     created_at = models.DateTimeField(default=timezone.now)
     updated_at = models.DateTimeField(auto_now=True)
-    devices = models.ManyToManyField(Device, related_name='payments')
+    devices = models.ManyToManyField(Device, related_name="payments")
 
     def __str__(self):
         return f"Payment by {self.user}"
 
+
 class BillFormula(models.Model):
-    id = models.CharField(primary_key=True, max_length=255)
     formula = models.CharField(max_length=255)
     base_amount = models.FloatField()
     discount_percentage = models.FloatField()
@@ -39,10 +41,11 @@ class BillFormula(models.Model):
     def __str__(self):
         return self.formula
 
+
 class Topup(models.Model):
-    id = models.CharField(primary_key=True, max_length=255)
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
     amount = models.FloatField()
-    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='topups')
+    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name="topups")
     paid = models.BooleanField(default=False)
     created_at = models.DateTimeField(default=timezone.now)
     updated_at = models.DateTimeField(auto_now=True)