Implement Typesense-based session service

[amedeorizzo]

Introduce a new session service utilizing Typesense for state management and session handling.

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[gemini-code-assist]

Summary of Changes

Hello @amedeorizzo, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly enhances the application's session management capabilities by integrating Typesense as a new, highly performant session service. This provides an alternative to the existing database-backed solution, offering flexibility in choosing the underlying storage for session data and events. The change also includes a refactoring of common state manipulation utilities, making them reusable across different session service implementations.

Highlights

• New Session Service: Introduced a new TypesenseSessionService for managing session state and events using Typesense as the backend.
• Dependency Update: Added typesense>=1.1.1 as a new dependency in pyproject.toml to support the new service.
• State Utility Refactoring: Moved state extraction and merging logic (extract_state_delta and merge_state) from database_session_service.py into _session_util.py to be shared across different session service implementations.
• Database Session Service Update: The existing DatabaseSessionService was updated to use the newly refactored state utility functions from _session_util.py.

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[gemini-code-assist]

Code Review

This pull request introduces a new TypesenseSessionService for session management and refactors some shared state logic into a utility module. The implementation is quite thorough. My review focuses on a critical security vulnerability related to the use of pickle, a high-severity bug in session listing that could lead to data truncation, and several medium-severity suggestions to improve code consistency, clarity, and adherence to best practices.