Add ConfigMergerTrait so app config overrides module defaults

[rsd]

Why

Reusable modules need defaults while letting each app override. Today, when keys collide, module config wins.
Opt-in only; existing behavior unchanged unless providers call the new helper.

What

• New Nwidart\Modules\Traits\ConfigMergerTrait
• mergeConfigDefaultsFrom($path, $key, $existingPrecedence = true, $deep = true)
  • App (existing) config wins by default
  • Deep merge (default) via array_replace_recursive, or shallow via array_merge
  • No-op when config is cached

Usage (in a module ServiceProvider)

use Nwidart\Modules\Traits\ConfigMergerTrait;

class ModuleServiceProvider extends ServiceProvider
{
    use ConfigMergerTrait;

    protected function registerConfig(): void
    {
        $configPath = module_path($this->name, config('modules.paths.generator.config.path'));

        if (is_dir($configPath)) {
            $iterator = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($configPath));

            foreach ($iterator as $file) {
                if ($file->isFile() && $file->getExtension() === 'php') {
                    $config = str_replace($configPath.DIRECTORY_SEPARATOR, '', $file->getPathname());
                    $config_key = str_replace([DIRECTORY_SEPARATOR, '.php'], ['.', ''], $config);
                    $segments = explode('.', $this->nameLower.'.'.$config_key);

                    // remove duplicated adjacent segments
                    $normalized = [];
                    foreach ($segments as $segment) {
                        if (end($normalized) !== $segment) $normalized[] = $segment;
                    }

                    $key = ($config === 'config.php') ? $this->nameLower : implode('.', $normalized);

                    $this->publishes([$file->getPathname() => config_path($config)], 'config');
                    $this->mergeConfigDefaultsFrom($file->getPathname(), $key); // app wins (deep) by default
                }
            }
        }
    }
}