feat(sessions): Add session title management functionality

[zhangp365]

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: #1825 #1340 #1372
• Related:

Problem: There is no title field in the sessions table, so when the frontend tries to display the chat history to users, there are no readable titles in the history list. In contrast, when users interact with other agents, the history list always contains readable titles.

Solution: This update introduces the ability to set, update, and clear titles for user sessions across various session services. The following changes were made:

• Added title attribute to the Session model.
• Implemented update_session_title method in BaseSessionService and its concrete implementations (e.g., DatabaseSessionService, InMemorySessionService, SqliteSessionService, VertexAiSessionService).
• Updated the adk_web_server.py to include a new endpoint for updating session titles.
• Enhanced migration scripts to accommodate the new title field in session records.
• Added unit tests to verify the functionality of session title management.

Unit Tests

• [x] I have added or updated unit tests for this change.
• [x] All unit tests pass locally.

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Manual End-to-End (E2E) Tests

I have installed the updated code on both my local machine and my server, started adk web, and run the agent. Everything works as expected with no issues.

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Checklist

• [x] I have read the CONTRIBUTING.md document.
• [x] I have performed a self-review of my code.
• [x] I have added comments where the code may be difficult to understand.
• [x] I have added tests that prove my fix is effective or that my feature works.
• [x] All new and existing unit tests pass locally with my changes.
• [x] I have manually tested my changes end-to-end.
• [x] Any dependent changes have been merged and published in downstream modules.

[gemini-code-assist[bot]]

Summary of Changes

Hello @zhangp365, I'm Gemini Code Assist[^1]! 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 introduces a crucial feature for user experience by enabling the management of titles for user sessions. Previously, chat histories lacked readable titles, making it difficult for users to distinguish between different sessions. This change addresses that by integrating a title field into the session model and providing the necessary API and service layer functionality to set, update, and clear these titles, ensuring a consistent and user-friendly experience across all session types.

Highlights

• Session Model Enhancement: The Session model now includes an optional title attribute, allowing for human-readable names for user sessions.
• API Endpoint for Title Management: A new PATCH endpoint /apps/{app_name}/users/{user_id}/sessions/{session_id}/title has been added to adk_web_server.py to enable updating session titles.
• Service Layer Integration: The update_session_title method has been introduced in BaseSessionService and implemented across all concrete session service types (Database, In-Memory, SQLite, and Vertex AI) to support title creation, retrieval, and modification.
• Database Schema Updates: Database-backed session services (Database and SQLite) have been updated to include a title column in their respective session storage schemas, with migration scripts adjusted to handle this new field.
• Comprehensive Unit Testing: Extensive unit tests have been added and updated to cover the new session title management functionality across all supported session service implementations, including edge cases like clearing titles and handling non-existent sessions.

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[ryanaiagent]

Hi @zhangp365 , Thank you for your work on this pull request. We appreciate the effort you've invested. Can you please fix the failing unit tests before we proceed with the review.

[zhangp365]

Hi @zhangp365 , Thank you for your work on this pull request. We appreciate the effort you've invested. Can you please fix the failing unit tests before we proceed with the review.

have fixed it.