migration(billing): Add expires_at field and is_expired property to Topup model for expiration management 🔧

billing/models.py

@@ -53,9 +53,16 @@ class Topup(models.Model):
     paid = models.BooleanField(default=False)
     paid_at = models.DateTimeField(null=True, blank=True)
     mib_reference = models.CharField(default="", null=True, blank=True)
+    expires_at = models.DateTimeField(null=True, blank=True)
     created_at = models.DateTimeField(default=timezone.now)
     updated_at = models.DateTimeField(auto_now=True)
 
+    @property
+    def is_expired(self):
+        if self.expires_at is None:
+            return False
+        return timezone.now() > self.expires_at
+
     def __str__(self):
         return f"Topup for {self.user}"