Apicurio/apicurio-registry

A JSON body that fails to deserialize on a ccompat endpoint gets a v3 ProblemDetails error instead of the Confluent {error_code, message} shape, and the response leaks the server exception class name. Follow-up from #10150 (review item O1), which moved the API-surface dispatch into ApiSurfaceResolver but intentionally left this mapper out of scope. Reproduce On current main, against a running registry: POST /apis/ccompat/v7/subjects/{subject}/versions Content-Type: application/json {"schema": {"not": "a string"}} returns 400: {"detail":"BadRequestException: Cannot deserialize value of type `java.lang.String` from Object value (token `JsonToken.START_OBJECT`)","title":"Cannot deserialize value of type `java.lang.String` from Object value (token `JsonToken.START_OBJECT`)","status":400,"name":"BadRequestException"} By contrast, a ccompat 404 from the same API correctly returns {"message":"Subject 'does-not-exist' not found.","error_code":40401}. Cause app/src/main/java/io/apicurio/regis

Part of #10297. Can start now. Held until Wednesday 14 October for a contributor who asked about this work earlier. After that, anyone can claim it with /assign-me. The Confluent-compatible endpoints /compatibility/subjects/{subject}/versions/{version} accept verbose, documented as "includes reason when compatibility fails", but ignore it (P7). CompatibilityResourceImpl (v7) catches the RuleViolationException and returns only is_compatible: false. Confluent's client reads messages, and falls back to "Schemas are incompatible" without it. Work Add messages (array of strings) to CompatibilityCheckResponse in the ccompat v7 and v8 OpenAPI documents. With verbose=true, fill it from the violation's causes, e.g. "<description> at <context>"; without it, leave it out, as Confluent does. Check the v8 delegate copies the field. Done when ConfluentClientTest asserts the messages returned to Confluent's client for an incompatible schema with verbose=true, and their absence without it.

Part of #10297. Waits for #10472. Uses #10471's endpoint; until it's merged, mock it. Work For a cause with a code, fetch its explanation from #10471 on demand (not for every cause up front), and cache it for the session. Help: render it as Markdown. It must be sanitised: use marked and DOMPurify, which the UI already gets through Monaco, as direct dependencies. Examples: show them as schema pairs, using the diff editor. 404 or no code: show nothing extra. Done when A Playwright test with a mocked explanation: help and an example are shown, and a cause without a code shows none.

Part of #10297. Waits for #10472; works with today's context and picks up the new pointers when present. Work Pointer to text: map a JSON Pointer to a text range on the text as displayed. The Content tab pretty-prints JSON and can convert to YAML, so ranges must come from the displayed text. yaml's parseDocument (already a dependency) handles both. Walk the pointer and fall back to the deepest part that resolves (P6). Markers: Monaco markers on each cause's range (RegistryEditors.tsx exposes the editor through onMount), and a click on a cause scrolls to it. Both sides: use proposed.pointer and existing.pointer when present, with context as the proposed pointer otherwise. Show both documents through the existing diff editor (DiffView). Under a FULL level, show each cause's direction. Referenced artifacts: a location with a reference is in a referenced artifact. Don't apply its pointer to the main document; list it without a highlight (showing the referenced artifact can come later). No

Part of #10297. Can start now; doesn't need the new API fields. Held until Wednesday 14 October for a contributor who asked about this work earlier. After that, anyone can claim it with /assign-me. Rule violations are shown by InvalidContentModal (ui/ui-app/src/app/components/modals/) as a flat list: context in bold, description under it. The content the user submitted is discarded before the error arrives (P5): ArtifactPage and GroupPage close the modal before the request, and the create and test modals reset on reopen. Work Keep the content: keep the submitted content and its content type with the error, in every flow that can get a rule violation: create artifact, create version, test (dry run), finalize draft (see the flows listed in #10297). The report: a component for compatibility violations, which replaces the list in InvalidContentModal for them: causes grouped by location; the submitted content shown read-only, with a way to show the version it was compared against, when kn