Handle subscribe renew date, langchain, pydantic & logger.warn warnings

- Ensure langchain less than 0.2.0 is used, to prevent breaking
  ChatOpenAI, PyMuPDF usage due to their deprecation after 0.2.0
- Set subscription renewal date to a timezone aware datetime
- Use logger.warning instead of logger.warn as latter is deprecated
- Use `model_dump' not deprecated dict to get all configured content_types

tests/helpers.py

@@ -1,6 +1,8 @@
 import os
+from datetime import datetime
 
 import factory
+from django.utils.timezone import make_aware
 
 from khoj.database.models import (
     ChatModelOptions,
@@ -90,4 +92,4 @@ class SubscriptionFactory(factory.django.DjangoModelFactory):
     user = factory.SubFactory(UserFactory)
     type = "standard"
     is_recurring = False
-    renewal_date = "2100-04-01"
+    renewal_date = make_aware(datetime.strptime("2100-04-01", "%Y-%m-%d"))