Add Session `title`

[simonwei97]

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Contribution guide.

Is your feature request related to a problem? Please describe.

Up to now, session display with an UUID. If users have lots of sessions, session display bar is not clearly for user to know this or that session topic.

Describe the solution you'd like

After create session, title is empty. Once user chat with target agent in someone session, session title will be updated after event generated.

==== session display bar ===
- Hello
- What'is the weather like tody in New York?
- ADK Analysis
...
==== session display bar ===

Assumption

Describe alternatives you've considered

Tip

Which parts should be changed as we expected?

• Modify Session Models definition
• Moidfy FastAPI App api for Session management.
• Modify Session storage management.

Additional context

N/A

[simonwei97]

Another Approach ?

Storage title in the Sesssion.state.

https://github.com/google/adk-python/blob/main/src/google/adk/sessions/session.py#L52

Then may should modify Session service function list_sessions, set exist state rather than empty dict(now version, same as v1.2.1) before function return.

adk-python/src/google/adk/sessions/database_session_service.py

Lines 481 to 502 in 0a5cf45

	@override
	async def list_sessions(
	self, *, app_name: str, user_id: str
	) -> ListSessionsResponse:
	with self.database_session_factory() as session_factory:
	results = (
	session_factory.query(StorageSession)
	.filter(StorageSession.app_name == app_name)
	.filter(StorageSession.user_id == user_id)
	.all()
	)
	sessions = []
	for storage_session in results:
	session = Session(
	app_name=app_name,
	user_id=user_id,
	id=storage_session.id,
	state={},
	last_update_time=storage_session.update_time.timestamp(),
	)
	sessions.append(session)
	return ListSessionsResponse(sessions=sessions)

[Jacksunwei]

@DeanChensj this would be a general feature for session service.

[meher-gajula]

#1825, please review if the PR fixes this.