Add default settings to let new users be subscribed on trial

- Add the default user to a subscription trial
- Update associated unit tests

src/database/adapters/__init__.py

@@ -101,6 +101,8 @@ async def create_google_user(token: dict) -> KhojUser:
         user=user,
     )
 
+    await Subscription.objects.acreate(user=user, type="trial")
+
     return user