Feature/i18n permalinks

[MamlukiSn]

Description

This PR enables the translation of permalinks.
Useful when frontend URL's are also translated based on the locale.

Usage

1. Allows localization of the permalinkBase property of the ModuleController

//return an array from the getLocalizedPermalinkBase controller method with the keys being locales
//the slug attribute will be appended to the value

/**
* @return array
*/
protected function getLocalizedPermalinkBase()
{
    return [
        'en' => 'collection/artists',
        'fr' => 'collection/artistes',
    ];
}

2. Allow localization of the customPermalink property by use of localizedCustomPermalink property instead

//pass localizedCustomPermalink to the form data which is an array with the keys being locales and values being the translated urls
protected function formData($request)
{
    return [
        'localizedCustomPermalink' => [
            'en' =>'https://website.com/en/news',
            'fr' =>'https://website.com/fr/nouvelles',
        ],
    ];
}

[daun]

Nice to see somebody tackle this!

To follow the way other Twill features are handled, the localized permalinks should probably be supplied through a method on the controller, similar to the original getPermalinkBaseUrl method. E.g. getLocalizedPermalinkBaseUrls. Requiring the json_encode in every controller is error-prone and a separate method would make it easy to see what that code is doing. The array can be converted to json in blade.

[pboivin]

Hi @MamlukiSn, this is cool! I believe it's the final missing piece for fully configurable permalinks in TitleEditor.

I've added a few questions and comments below.