Create API webhook, endpoints for subscription payments using Stripe

- Add fields to mark users as subscribed to a specific plan and
  subscription renewal date in DB
- Add ability to unsubscribe a user using their email address
- Expose webhook for stripe to callback confirming payment

src/database/adapters/__init__.py

@@ -1,5 +1,5 @@
 from typing import Type, TypeVar, List
-from datetime import date
+from datetime import date, datetime, timedelta
 import secrets
 from typing import Type, TypeVar, List
 from datetime import date
@@ -103,6 +103,27 @@ async def create_google_user(token: dict) -> KhojUser:
     return user
 
 
+async def set_user_subscribed(email: str, type="standard") -> KhojUser:
+    user = await KhojUser.objects.filter(email=email).afirst()
+    if user:
+        user.subscription_type = type
+        start_date = user.subscription_renewal_date or datetime.now()
+        user.subscription_renewal_date = start_date + timedelta(days=30)
+        await user.asave()
+        return user
+    else:
+        return None
+
+
+def is_user_subscribed(email: str, type="standard") -> bool:
+    user = KhojUser.objects.filter(email=email, subscription_type=type).first()
+    if user and user.subscription_renewal_date:
+        is_subscribed = user.subscription_renewal_date > date.today()
+        return is_subscribed
+    else:
+        return False
+
+
 async def get_user_by_token(token: dict) -> KhojUser:
     google_user = await GoogleUser.objects.filter(sub=token.get("sub")).select_related("user").afirst()
     if not google_user:

src/database/migrations/0013_khojuser_subscription_renewal_date_and_more.py

@@ -0,0 +1,24 @@
+# Generated by Django 4.2.5 on 2023-11-07 18:19
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("database", "0012_entry_file_source"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="khojuser",
+            name="subscription_renewal_date",
+            field=models.DateTimeField(default=None, null=True),
+        ),
+        migrations.AddField(
+            model_name="khojuser",
+            name="subscription_type",
+            field=models.CharField(
+                choices=[("trial", "Trial"), ("standard", "Standard")], default="trial", max_length=20
+            ),
+        ),
+    ]

src/database/models/__init__.py

@@ -14,7 +14,15 @@ class BaseModel(models.Model):
 
 
 class KhojUser(AbstractUser):
+    class SubscriptionType(models.TextChoices):
+        TRIAL = "trial"
+        STANDARD = "standard"
+
     uuid = models.UUIDField(models.UUIDField(default=uuid.uuid4, editable=False))
+    subscription_type = models.CharField(
+        max_length=20, choices=SubscriptionType.choices, default=SubscriptionType.TRIAL
+    )
+    subscription_renewal_date = models.DateTimeField(null=True, default=None)
 
     def save(self, *args, **kwargs):
         if not self.uuid: