fix: Add support for app in _init_session

PiperOrigin-RevId: 834389695

Author: Tongzhou-Jiang

vertexai/agent_engines/templates/adk.py

@@ -610,8 +610,9 @@ async def _init_session(
  auth = _Authorization(**auth)
  session_state[auth_id] = auth.access_token
 
+ app = self._tmpl_attrs.get("app")
  session = await session_service.create_session(
- app_name=self._tmpl_attrs.get("app_name"),
+ app_name=app.name if app else self._tmpl_attrs.get("app_name"),
  user_id=request.user_id,
  state=session_state,
  )
@@ -628,7 +629,7 @@ async def _init_session(
  ):
  version_data = _ArtifactVersion(**version_data)
  saved_version = await artifact_service.save_artifact(
- app_name=self._tmpl_attrs.get("app_name"),
+ app_name=app.name if app else self._tmpl_attrs.get("app_name"),
  user_id=request.user_id,
  session_id=session.id,
  filename=artifact.file_name,