Missing API reference for `DatabaseSessionService`

[olliefr]

The API Reference for google.adk.sessions module no longer mentions DatabaseSessionService at all.

I think this has to do with lazy loading of DatabaseSessionService:

src/google/adk/sessions/__init__.py

I have a feeling that your docs generator fails to comprehend the deferred import (via __getattr__) but it's not my area of expertise, really, so it's just a guess.