Fix TodolistOrGroup union deserialization for Get/Update

[jeremy]

Summary

• Fix broken union deserialization in todolists and todolist groups Get() and Update() methods. The API returns flat JSON ({"id": 123, "type": "Todolist", ...}) but the generated AsTodolistOrGroup0/1() methods expect envelope-wrapped variants ({"todolist": {...}}), yielding zero-valued structs. Bypasses the union helpers by decoding resp.Body directly into the target generated type.
• Add httptest service contract tests for all four affected call sites. Each test asserts request method, URL path, response field population (ID, Name, Parent, Bucket, Creator), and for Update also validates the JSON request body payload.

Go-only containment fix — no changes to the shared openapi.json.

Test plan

• go test ./pkg/basecamp/... — 4 new service-level tests pass
• go test ./... — full Go test suite passes
• make check — all cross-SDK checks pass (Smithy, Go, TS, Ruby, Kotlin, Swift, conformance)

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Summary by cubic

Fix union deserialization in todolists and todolist groups Get() and Update() by correctly parsing the flat JSON the API returns. Go-only fix; no changes to openapi.json.

• Bug Fixes

  • Decode resp.Body into generated.Todolist and generated.TodolistGroup instead of using AsTodolistOrGroup0/1.
  • Applies to Get() and Update() in TodolistsService and TodolistGroupsService.

• Tests

  • Added httptest contract tests for Get() and Update() in both services.
  • Tests assert HTTP method, path, key response fields, and request body for updates.

^{Written for commit d1a620b. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 4 files

[Copilot]

Pull request overview

Updates the Go Basecamp SDK’s todolist and todolist group services to correctly decode responses from the polymorphic /todolists/:id endpoint (which returns flat JSON), and adds httptest-based contract tests to lock in the expected request/response behavior.

Changes:

• Decode Get/Update responses by unmarshalling resp.Body into generated.Todolist / generated.TodolistGroup instead of using the union-envelope helpers.
• Add httptest contract tests for TodolistsService.Get/Update and TodolistGroupsService.Get/Update.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.

File	Description
go/pkg/basecamp/todolists.go	Switches Get/Update response decoding to unmarshal flat JSON from resp.Body.
go/pkg/basecamp/todolists_test.go	Adds httptest contract tests validating paths, request bodies, and basic response mapping for todolists.
go/pkg/basecamp/todolist_groups.go	Switches Get/Update response decoding to unmarshal flat JSON from resp.Body.
go/pkg/basecamp/todolist_groups_test.go	Adds httptest contract tests validating paths, request bodies, and basic response mapping for todolist groups.

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