✨ Compile WP args schema from #[Param] attribute on handler parameters

[dimitriBouteille]

Summary

Add #[Param] attribute on handler parameters so the args schema is compiled into WordPress's register_rest_route instead of being re-implemented inside every handler. WordPress now enforces required / type / enum / sanitize_callback before the handler runs, and the auto-discovery endpoint (/wp-json/<ns>) describes the route arguments.

Why

RouteLoader::buildRouteArgs() was always emitting 'args' => [], so:

• Validation had to be duplicated in every handler.
• Misuse (missing required field) hit the handler before being rejected.
• The discovery endpoint exposed nothing useful to API consumers.

Usage

#[Route('blog/v1', '/articles/(?P<id>\d+)')]
class ArticleRoute
{
    #[Action(Method::GET)]
    public function show(
        #[Param(required: true, description: 'Article identifier')]
        int $id,
        #[Param(default: 10, enum: [10, 25, 50])]
        int $perPage,
    ): \WP_REST_Response { ... }
}

Compiled into:

  'args' => [
      'id' => [
          'type' => 'integer',
          'required' => true,
          'description' => 'Article identifier',
          'sanitize_callback' => 'absint',
      ],
      'perPage' => [
          'type' => 'integer',
          'default' => 10,
          'enum' => [10, 25, 50],
          'sanitize_callback' => 'absint',
      ],
  ]

Type inference (when Param::$type is null)

Backward compatibility

Handlers without #[Param] keep registering with empty args — nothing else changes.