fix(templates): nest the REST endpoint so 'schema' survives register_rest_route()'s upgrade step (C)

[akshat009]

Closes the remaining half of item C from the open-issues report — the previous PR (#15) implemented get_item_schema() correctly but wired it into register_routes() at the wrong nesting level, so core silently dropped it.

The bug

register_rest_route() upgrades a flat args array to multiple endpoints whenever it sees a top-level 'callback' key — wrapping the entire array as a single numerically-indexed entry:

if ( isset( $args['callback'] ) ) {
    $args = array( $args );
}

'schema' was a sibling of 'callback' in that same flat array, so it got swallowed into that numeric entry along with everything else. get_data_for_route() looks for schema among the route's string keys, where it no longer existed — OPTIONS /wp-json/.../items kept returning no schema, the exact gap #15 was meant to close.

The fix

Nest the endpoint definition one level deeper and lift 'schema' out as a genuine route-level option, matching how core's own controllers do it (WP_REST_Settings_Controller et al):

register_rest_route(
    $this->namespace,
    '/' . $this->rest_base,
    array(
        array(
            'methods'             => \WP_REST_Server::READABLE,
            'callback'            => $this->get_items( ... ),
            'permission_callback' => $this->get_items_permissions_check( ... ),
            'args'                => array( /* … */ ),
        ),
        'schema' => $this->get_public_item_schema( ... ),
    )
);

get_item_schema() and the tests/bootstrap.php stub extension from #15 were both already correct and are untouched.

Regression test

The existing test_register_routes only asserts the third argument is an array (Mockery::type('array')), which passes regardless of nesting — it could not have caught this. Added a test that spies on the actual call:

public function test_register_routes_exposes_schema_as_a_route_option(): void {
    Functions\expect( 'register_rest_route' )
        ->once()
        ->andReturnUsing( function ( $route_namespace, $route, $args ) {
            $this->assertArrayHasKey( 'schema', $args, '...' );
            $this->assertArrayHasKey( 0, $args, '...' );
            return true;
        } );

    ( new Rest_Controller() )->register_routes();
}

Verification

• npm test (CLI's own suite): 69/69.
• Real end-to-end run against a generated --modules rest_api,caching scaffold:
  • composer test → 13/13 PHPUnit tests, 19 assertions (was 12/12 before this regression test).
  • composer lint → 15/15 files, 0 errors / 0 warnings. First run flagged the new test's closure parameter named $namespace as a reserved-keyword warning (WPCS NoReservedKeywordParameterNames) — caught by that same lint run and fixed by renaming to $route_namespace before landing.

D (test suite depth) remains out of scope, per the report.

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