…project#11796)

# Description

`POST .../providers/Radius.Core/applications/{app}/getGraph` returned
404 because the namespace builder for `Radius.Core` never wired the
`getGraph` custom action — only `Applications.Core/applications` did.
The OpenAPI route exists but had no controller, blocking app graph
rendering in the dashboard.

- **New controller**: `GetGraphv20250801preview` in
`pkg/corerp/frontend/controller/applications/v20250801preview/getgraph.go`
(package `v20250801preview`). Placed in a `v20250801preview/` subpackage
to match the convention established by
`pkg/corerp/frontend/controller/environments/v20250801preview/`. Typed
against `datamodel.Application_v20250801preview` and uses the
`Application20250801*` converters.
- **Shared helper**: Extracted a `ComputeGraphResponse` exported helper
in the parent `pkg/corerp/frontend/controller/applications` package so
both the `Applications.Core` and `Radius.Core` getGraph controllers
reuse the same graph-listing logic (resource type discovery,
application-/environment-scoped listing, and graph computation) without
duplication.
- **Stricter validation**: `ComputeGraphResponse` uses
`resources.ParseResource` (instead of `resources.Parse`) to validate the
environment ID is a named resource, rejecting collection or
custom-action IDs. The error is wrapped with `fmt.Errorf` for context.
- **Wiring**: `SetupRadiusCoreNamespace` in `pkg/corerp/setup/setup.go`
now registers `Custom["getGraph"]` on the `applications` resource,
analogous to the `Applications.Core/applications` registration.
- **Tests**: Unit test for the not-found path on the new controller,
plus a router assertion in `setup_test.go` that `POST
.../radius.core/applications/app0/getgraph` resolves to
`ACTIONGETGRAPH`. Additional tests targeting the lines flagged by
Codecov:
  - `ComputeGraphResponse` invalid-environment-ID error path.
- `ComputeGraphResponse` UCP error-propagation path, driven by an
`httptest` UCP server returning 500 on `/planes/radius/local/providers`.
- `ComputeGraphResponse` `listAllResourcesByApplication` error path
(lines 62-63), driven by an `httptest` server returning a resource type
then failing on `GetProviderSummary`.
- `ComputeGraphResponse` `listAllResourcesByEnvironment` error path
(lines 67-68), driven by an `httptest` server where application-scoped
listing succeeds but environment-scoped listing returns 500.
- Database error path through `GetGraph.Run` and
`GetGraphv20250801preview.Run` (non-`NotFound` `Get` error is
propagated).
- End-to-end success path through both `Run` methods into
`ComputeGraphResponse`, driven by an `httptest` UCP server returning an
empty providers list to yield an empty graph.

Coverage on the new shared helper rose from 0% to ~87.5%, both `Run`
methods are at 100%, and the `v20250801preview` getGraph package is at
100%.

```go
Custom: map[string]builder.Operation[datamodel.Application_v20250801preview]{
    "getGraph": {
        APIController: func(opt apictrl.Options) (apictrl.Controller, error) {
            return app_v20250801_ctrl.NewGetGraphv20250801preview(opt, *recipeControllerConfig.UCPConnection)
        },
    },
},
```

## Type of change

- This pull request fixes a bug in Radius and has an approved issue
(issue link required).

## Contributor checklist
Please verify that the PR meets the following requirements, where
applicable:

- An overview of proposed schema changes is included in a linked GitHub
issue.
    - [ ] Yes
    - [x] Not applicable
- A design document is added or updated under `eng/design-notes/` in
this repository, if new APIs are being introduced.
    - [ ] Yes
    - [x] Not applicable
- The design document has been reviewed and approved by Radius
maintainers/approvers.
    - [ ] Yes
    - [x] Not applicable
- A PR for
[resource-types-contrib](https://github.com/radius-project/resource-types-contrib/)
is created, if resource types or recipes are affected by the changes in
this PR.
    - [ ] Yes
    - [x] Not applicable
- A PR for [dashboard](https://github.com/radius-project/dashboard/) is
created, if the Radius Dashboard is affected by the changes in this PR.
    - [ ] Yes
    - [x] Not applicable
- A PR for the [documentation
repository](https://github.com/radius-project/docs) is created, if the
changes in this PR affect the documentation or any user facing updates
are made.
    - [ ] Yes
    - [x] Not applicable

---------

Signed-off-by: Will <28876888+willtsai@users.noreply.github.com>
Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: willtsai <28876888+willtsai@users.noreply.github.com>
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
Signed-off-by: Reshma Abdul Rahim <reshmarahim.abdul@microsoft.com>