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

pyproject.toml

@@ -55,7 +55,7 @@ dependencies = [
     "torch == 2.0.1",
     "uvicorn == 0.17.6",
     "aiohttp ~= 3.9.0",
-    "langchain >= 0.0.331",
+    "langchain <= 0.2.0",
     "requests >= 2.26.0",
     "bs4 >= 0.0.1",
     "anyio == 3.7.1",