feat(form-builder): extend public form backend for S3a PR 2

- Seed AVAILABILITY_PICKER and SECTION_PRIORITY demo fields in the
  event_registration showcase, and augment seedEchtFeesten with a
  parent-level VOLUNTEER time slot pair + a standard registration-
  visible section whose name duplicates a child section so the
  PublicFormController dedup path is exercised end-to-end.
- Validate SECTION_PRIORITY value shape in FormValueService: arrays of
  { section_id, priority } with unique section_ids + priorities in 1..5,
  max 5 entries, and section_ids scoped to the schema's event tree
  (parent + children). Error envelope is the standard VALIDATION_FAILED
  FieldValidationException shape so the portal renders errors next to
  the field.
- Enrich admin-facing FormSubmissionResource with a nested identity_match
  block mirroring the PublicFormSubmissionResource contract (status only;
  leaves room for future matched_user_id / confidence).
- Lock in the FORM-05 stub contract with 6 tests against the existing
  TriggerPersonIdentityMatchOnFormSubmit listener (no new listener was
  needed — the current one already writes 'pending' for public
  event_registration submissions per ARCH §31.1).
- 24 new backend assertions across seeder, shape validation, listener
  state matrix, and resource serialisation.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/tests/Feature/FormBuilder/FormSubmissionResourceIdentityMatchTest.php

@@ -0,0 +1,100 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Feature\FormBuilder;
+
+use App\Enums\FormBuilder\FormSubmissionStatus;
+use App\Http\Resources\FormBuilder\FormSubmissionResource;
+use App\Models\FormBuilder\FormSchema;
+use App\Models\FormBuilder\FormSubmission;
+use App\Models\Organisation;
+use App\Models\User;
+use Database\Seeders\RoleSeeder;
+use Illuminate\Foundation\Testing\RefreshDatabase;
+use Laravel\Sanctum\Sanctum;
+use Tests\TestCase;
+
+/**
+ * Admin-facing FormSubmissionResource must surface identity_match_status
+ * as a nested { status } block so the organiser UI can render the same
+ * signal shape the portal already exposes. Keeps room for future
+ * matched_user_id / confidence fields without a contract break.
+ */
+final class FormSubmissionResourceIdentityMatchTest extends TestCase
+{
+    use RefreshDatabase;
+
+    private Organisation $org;
+
+    private FormSchema $schema;
+
+    private User $admin;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->seed(RoleSeeder::class);
+
+        $this->org = Organisation::factory()->create();
+        $this->schema = FormSchema::factory()->create(['organisation_id' => $this->org->id]);
+        $this->admin = User::factory()->create();
+        $this->org->users()->attach($this->admin, ['role' => 'org_admin']);
+    }
+
+    private function toArray(FormSubmission $submission): array
+    {
+        $request = request();
+        Sanctum::actingAs($this->admin);
+
+        return (new FormSubmissionResource($submission->fresh()))->toArray($request);
+    }
+
+    public function test_pending_status_serialises_as_nested_object(): void
+    {
+        $submission = FormSubmission::create([
+            'form_schema_id' => $this->schema->id,
+            'status' => FormSubmissionStatus::SUBMITTED->value,
+            'submitted_at' => now(),
+            'is_test' => false,
+            'identity_match_status' => 'pending',
+        ]);
+
+        $array = $this->toArray($submission);
+
+        $this->assertIsArray($array['identity_match']);
+        $this->assertSame(['status' => 'pending'], $array['identity_match']);
+    }
+
+    public function test_null_status_serialises_as_null(): void
+    {
+        $submission = FormSubmission::create([
+            'form_schema_id' => $this->schema->id,
+            'status' => FormSubmissionStatus::SUBMITTED->value,
+            'submitted_at' => now(),
+            'is_test' => false,
+        ]);
+
+        $array = $this->toArray($submission);
+
+        $this->assertNull($array['identity_match']);
+    }
+
+    public function test_api_endpoint_returns_matching_shape(): void
+    {
+        Sanctum::actingAs($this->admin);
+
+        $submission = FormSubmission::create([
+            'form_schema_id' => $this->schema->id,
+            'status' => FormSubmissionStatus::SUBMITTED->value,
+            'submitted_at' => now(),
+            'is_test' => false,
+            'identity_match_status' => 'matched',
+        ]);
+
+        $response = $this->getJson("/api/v1/organisations/{$this->org->id}/forms/submissions/{$submission->id}");
+
+        $response->assertOk()
+            ->assertJsonPath('data.identity_match.status', 'matched');
+    }
+}