Generic form system: grants backend integration (PR 3/5)

[marcoacierno]

Summary

Third PR of the stack (stacked on #4707 ← #4705). Wires grants to the generic form engine — fully backward compatible on the wire: the deployed frontend keeps working unchanged.

• Grant.form_answer: nullable OneToOne to generic_forms.FormAnswer (SET_NULL); the 4 still-required soft columns (why, python_usage, been_to_other_events, occupation) become blank=True. Columns stay NOT NULL — the mutation layer never writes None.
• sendGrant/updateGrant: the soft-question fields become optional; new optional answers: JSON map (question_id → value).
  • Dynamic question set = 6: why, python_usage, been_to_other_events, community_contribution, age_group, notes. gender and occupation stay structured — grants/summary.py aggregates both columns for the grant summary reporting (caught in review by @marcoacierno); they remain optional inputs that coalesce to "" when omitted.
  • Legacy path (no answers): behavior byte-identical — soft-field required/max-length checks unchanged, regression-tested.
  • Answers path: validated via generic_forms.validate_answers against the conference's GRANT form; rejected with a clear error when no form is configured; per-question failures returned in a new answersErrors: JSON map on GrantErrors (dynamic question ids can't be static fields; add_error only appends to typed lists, so the map is assigned directly).
  • FormAnswer persisted (versioned envelope) via update_or_create inside the existing @transaction.atomic, linked from the grant.
• Grant.formAnswers: JSON | null exposes the flat answers map for the edit-flow prefill (from_model attaches the relation — me.grant returns a detached instance).

Test plan

• Named test sending the exact post-cutover frontend payload (answers map, dynamic fields omitted) end-to-end → Grant + linked FormAnswer, empty dynamic columns, gender/occupation persisted
• Defensive tests: answers payload omitting gender/occupation stores "" (never None into NOT NULL columns), on both create and update
• Invalid answers → answersErrors per question, nothing persisted; answers-without-form rejected; update path reuses the existing FormAnswer (no duplicates); legacy soft columns untouched by answers updates
• All pre-existing grants tests green unmodified (legacy-shape regression proof)
• Full suite 1208 passed; ruff + format clean

Deploy note

After this merges to main: deploy to staging (pastaporto) via workflow_dispatch — PR5's frontend CI codegens against the staging schema and needs answers/answersErrors/formAnswers live there.

Stack: #4705 → #4707 → PR3 (this) → PR4 admin display/export → PR5 frontend.

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Project	Deployment	Actions	Updated (UTC)
pycon	Ready	Preview	Aug 7, 2026 2:44am

[claude]

Wires Grant mutations to the generic form engine: adds Grant.form_answer (nullable OneToOne to generic_forms.FormAnswer), makes the legacy soft-question inputs optional, and adds an answers/answersErrors path validated against the conference's GRANT form.

Validation regression for the legacy (no-generic-form) path

age_group and occupation used to be non-nullable enum fields on SendGrantInput/UpdateGrantInput (backend/api/grants/mutations.py), so the GraphQL schema itself guaranteed a valid, non-empty value. They're now AgeGroup | None = None / Occupation | None = None to support the answers path, but BaseGrantInput.validate() only backfills why, python_usage, been_to_other_events into non_empty_fields when not uses_answers (mutations.py:133-135). age_group/occupation/gender were left out, so a conference that has not configured a generic form (uses_answers is False) can now submit/update a grant with age_group/occupation omitted entirely, silently persisted as "". Previously this was impossible to express over the API. Since grants/summary.py aggregates these columns for reporting, blank values there will now be silently possible for legacy conferences. Worth adding these three back to the required-field check when not uses_answers, and a regression test for it (existing test suite doesn't cover this since it was previously enforced by the schema, not app logic).

Minor: redundant Form query

BaseGrantInput.validate() already fetches Form.objects.filter(conference=..., purpose=Form.Purpose.GRANT).first() to validate answers, then _persist_form_answer() re-fetches the same row with Form.objects.get(...) inside the mutation. Not a correctness issue, just an avoidable extra query per submission.

[codecov]

Codecov Report

❌ Patch coverage is 98.64865% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.49%. Comparing base (321f30f) to head (4528916).

Additional details and impacted files

@@                        Coverage Diff                         @@
##           generic-forms/02-graphql-query    #4709      +/-   ##
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+ Coverage                           92.47%   92.49%   +0.02%     
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  Files                                 359      359              
  Lines                               10921    10970      +49     
  Branches                              852      863      +11     
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+ Hits                                10099    10147      +48     
  Misses                                706      706              
- Partials                              116      117       +1     

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