chore(user-interviews): address facade isolation review nits

[pauldambra]

Problem

Follow-up nits from the review of #59132 (the user_interviews facade + contracts isolation PR):

• facade/contracts.py used stdlib dataclasses.dataclass — the recent architecture guidance prefers pydantic.dataclasses.dataclass so contracts get runtime validation at construction time.
• facade/__init__.py and presentation/__init__.py were empty, which CLAUDE.md discourages.
• The facade implemented business logic inline (regex parsing + ORM query) — facades should stay thin and call logic.py.

Changes

• Swap dataclasses.dataclass for pydantic.dataclasses.dataclass in products/user_interviews/backend/facade/contracts.py.
• Add products/user_interviews/backend/logic.py containing parse_interviewee_identifier and has_replied (the regex + ORM call). The facade now just delegates.
• Populate facade/__init__.py with public re-exports (mirrors the experiments facade convention) and add a docstring to presentation/__init__.py.

Public facade surface (parse_interviewee_identifier, has_replied, IntervieweeIdentity) is unchanged, so callers in posthog/api/sharing.py and presentation/views.py keep working as-is.

How did you test this code?

I'm an agent — no manual testing performed. Existing automated coverage in products/user_interviews/backend/test_facade.py exercises both functions through the facade and should continue to pass unchanged.

Publish to changelog?

no

🤖 Agent context

Authored by PostHog Code (an agent) in response to the human author asking it to apply three specific review comments from #59132. Decisions:

• Kept the facade as plain functions (not a class) since the existing surface was function-based and the upstream callers import the functions directly.
• Used pydantic.dataclasses.dataclass rather than pydantic.BaseModel — products/architecture.md describes this as the preferred upgrade over stdlib dataclasses, and IntervieweeIdentity has no need for BaseModel-only features.
• Followed the experiments product's facade/__init__.py shape (re-exports + __all__) and the error_tracking product's presentation/__init__.py shape (single docstring) since both already match this codebase's existing conventions.

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Created with PostHog Code

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

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### Issue 1 of 1
products/user_interviews/backend/logic.py:12
**`logic.py` imports from the `facade` package — dependency direction is inverted**

`logic.py` is the inner/lower layer; `facade/` is the outer layer that wraps it. Having `logic.py` import from `facade/contracts.py` means the lower layer depends on the upper layer, which is backwards. In practice this doesn't cause a circular import today (since `contracts.py` itself imports nothing from `logic`), but it makes the layering confusing and fragile — any future import added to `contracts.py` could create a cycle.

The fix is to move `IntervieweeIdentity` (and `contracts.py`) one level up to `products/user_interviews/backend/contracts.py` so that both `logic.py` and `facade/api.py` import it from a neutral sibling module. `facade/__init__.py` can continue to re-export it for the public surface.

_{Reviews (1): Last reviewed commit: "chore(user-interviews): address facade i..." | Re-trigger Greptile}

[stamphog]

A bot reviewer raised a valid unresolved concern: the new logic.py imports IntervieweeIdentity from facade/contracts.py, making the inner layer depend on the outer layer — the opposite of the intended direction. Per review policy, bot comments with valid concerns that go unaddressed require escalation.

[github-actions]

The bot's concern about inverted dependency direction was raised on an older commit and has been fully addressed: contracts.py was moved out of facade/ to backend/, so logic.py now imports from the sibling backend/contracts.py rather than from the outer facade/ layer. Dependency direction is now correct, and no showstoppers remain.

New commits pushed (delta classified non_trivial_delta) — stamphog approval dismissed; re-review running automatically.

[github-actions]

Clean facade isolation refactor — moves logic out of the facade into a dedicated layer, makes the facade thin, and wires up proper exports. The noted inverted dependency (logic.py importing IntervieweeIdentity from facade/contracts.py) is an architectural nit on a no-dependency frozen dataclass, not a functional or safety issue, and the inline concern is marked resolved.

[deployment-status-posthog]

Deploy status

Environment	Status	Deployed At	Workflow
dev	✅ Deployed	2026-05-20 20:18 UTC	Run
prod-us	✅ Deployed	2026-05-20 20:33 UTC	Run
prod-eu	✅ Deployed	2026-05-20 20:36 UTC	Run