## Summary
`PermissionsException` thrown by `SettingsPermissionGuard` (and other
permission code paths) was bubbling up through every typed REST
exception filter and landing in the global `UnhandledExceptionFilter`,
which falls back to **500** for anything that isn't an `HttpException`.
So a forbidden user (e.g. an API key whose role doesn't have
`DATA_MODEL`) calling `GET /rest/metadata/objects` got:
```
HTTP/1.1 500 Internal Server Error "Entity performing the request does not have permission"
```
GraphQL already had the right plumbing via
`permissionGraphqlApiExceptionHandler` (`ForbiddenError` → 403,
`UserInputError` → 400, `NotFoundError` → 404). This PR mirrors it on
the REST side.
## What
- New util `permissionRestApiExceptionCodeToHttpStatus` mapping every
`PermissionsExceptionCode` → HTTP status, with `assertUnreachable` to
force explicit handling of future codes.
- New filter `PermissionsRestApiExceptionFilter`
(`@Catch(PermissionsException)`) that delegates to
`HttpExceptionHandlerService.handleError(...)` with the resolved status.
- Wired `PermissionsRestApiExceptionFilter` (placed first, so the typed
filter wins over any sibling catch-all) into `@UseFilters(...)` of every
REST controller that uses `SettingsPermissionGuard` or whose service can
throw `PermissionsException`:
- `object-metadata`, `field-metadata`, `webhook`, `api-key`
- `view`, `view-sort`, `view-group`, `view-filter`, `view-filter-group`,
`view-field`
- `page-layout`, `page-layout-widget`, `page-layout-tab`
- `front-component`, `ai-generate-text`
- Unit tests covering 403 / 400 / 404 / 500 mappings.
## Mapping
| Code | Status |
|------|--------|
| `PERMISSION_DENIED`, `NO_AUTHENTICATION_CONTEXT`,
`ROLE_LABEL_ALREADY_EXISTS`, `CANNOT_UNASSIGN_LAST_ADMIN`,
`CANNOT_UPDATE_SELF_ROLE`, `CANNOT_DELETE_LAST_ADMIN_USER`,
`ROLE_NOT_EDITABLE`, `CANNOT_ADD_OBJECT_PERMISSION_ON_SYSTEM_OBJECT`,
`CANNOT_ADD_FIELD_PERMISSION_ON_SYSTEM_OBJECT` | **403** |
| `INVALID_ARG`, `INVALID_SETTING`,
`CANNOT_GIVE_WRITING_PERMISSION_ON_NON_READABLE_OBJECT`,
`CANNOT_GIVE_WRITING_PERMISSION_WITHOUT_READING_PERMISSION`,
`ONLY_FIELD_RESTRICTION_ALLOWED`,
`FIELD_RESTRICTION_ONLY_ALLOWED_ON_READABLE_OBJECT`,
`FIELD_RESTRICTION_ON_UPDATE_ONLY_ALLOWED_ON_UPDATABLE_OBJECT`,
`EMPTY_FIELD_PERMISSION_NOT_ALLOWED`,
`ROLE_MUST_HAVE_AT_LEAST_ONE_TARGET`, `ROLE_CANNOT_BE_ASSIGNED_TO_USERS`
| **400** |
| `ROLE_NOT_FOUND`, `OBJECT_METADATA_NOT_FOUND`,
`FIELD_METADATA_NOT_FOUND`, `FIELD_PERMISSION_NOT_FOUND`,
`PERMISSION_NOT_FOUND` | **404** |
| All remaining "internal" codes (rethrown as-is in GraphQL) | **500** |
## Before
<img width="507" height="216" alt="Screenshot 2026-05-19 at 19 26 07"
src="https://github.com/user-attachments/assets/21d633aa-7ee8-4923-94e4-7ad57258a29e"
/>
## After
<img width="610" height="385" alt="Screenshot 2026-05-19 at 19 26 01"
src="https://github.com/user-attachments/assets/0103b7ee-7df7-4aef-999a-73c22901afd2"
/>
