refactor(api): use sessionmaker in end user, retention & cleanup services

[carlos4s]

Summary

• Replace with Session(db.engine, expire_on_commit=False) + session.commit() with
  sessionmaker(bind=db.engine, expire_on_commit=False).begin() in end_user_service and messages_clean_service
• Replace with Session(db.engine).no_autoflush + session.commit() with
  sessionmaker(bind=db.engine, autoflush=False).begin() in clear_free_plan_tenant_expired_logs
• Updated test mocks to match new sessionmaker pattern

Part of #24245

Test plan

• ruff check passes
• 2482 unit tests pass

[github-actions]

Pyrefly Diff

base → PR

--- /tmp/pyrefly_base.txt	2026-04-08 19:22:13.055706706 +0000
+++ /tmp/pyrefly_pr.txt	2026-04-08 19:22:04.515686160 +0000
@@ -6399,9 +6399,9 @@
 ERROR Argument `FakeRepo` is not assignable to parameter `workflow_run_repo` with type `APIWorkflowRunRepository | None` in function `services.retention.workflow_run.clear_free_plan_expired_workflow_run_logs.WorkflowRunCleanup.__init__` [bad-argument-type]
    --> tests/unit_tests/services/test_clear_free_plan_expired_workflow_run_logs.py:114:49
 ERROR Class member `FixedDateTime.now` overrides parent class `datetime` in an inconsistent manner [bad-override]
-   --> tests/unit_tests/services/test_clear_free_plan_tenant_expired_logs.py:411:13
+   --> tests/unit_tests/services/test_clear_free_plan_tenant_expired_logs.py:407:13
 ERROR Class member `FixedDateTime.now` overrides parent class `datetime` in an inconsistent manner [bad-override]
-   --> tests/unit_tests/services/test_clear_free_plan_tenant_expired_logs.py:505:13
+   --> tests/unit_tests/services/test_clear_free_plan_tenant_expired_logs.py:501:13
 ERROR Argument `SimpleNamespace` is not assignable to parameter `account` with type `Account` in function `services.dataset_service.DatasetService.create_empty_dataset` [bad-argument-type]
    --> tests/unit_tests/services/test_dataset_service_dataset.py:310:93
 ERROR Argument `SimpleNamespace` is not assignable to parameter `account` with type `Account` in function `services.dataset_service.DatasetService.create_empty_dataset` [bad-argument-type]

[Copilot]

Pull request overview

Refactors several API services to use sessionmaker(...).begin() for transaction management instead of manually creating Session(...) objects and calling session.commit(), and updates unit tests to mock the new pattern.

Changes:

• Migrate EndUser and retention message cleanup flows to sessionmaker(...).begin() transaction contexts.
• Replace Session(...).no_autoflush usage in the free-plan log cleanup flow with sessionmaker(..., autoflush=False).begin().
• Update unit-test session mocks to emulate sessionmaker().begin() semantics.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
api/services/end_user_service.py	Switches EndUser DB interactions to sessionmaker(...).begin() and removes explicit commits.
api/services/retention/conversation/messages_clean_service.py	Uses sessionmaker(...).begin() for fetch/delete transactions and adjusts commit timing logic.
api/services/clear_free_plan_tenant_expired_logs.py	Replaces no_autoflush session usage with sessionmaker(..., autoflush=False).begin() and removes explicit commits.
api/tests/unit_tests/services/test_clear_free_plan_tenant_expired_logs.py	Updates monkeypatch/mocks to match the sessionmaker().begin() pattern.

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[Copilot]

commit_ms is now hard-coded to 0, but the transaction commit actually happens when the sessionmaker(...).begin() context exits. This makes the timing log misleading. Consider either (a) removing the commit timing from the log, or (b) restructuring to explicitly time the transaction end (e.g., measure around the context manager exit, or switch to a with sessionmaker(... )() as session: + explicit session.commit() if you need accurate commit timing).