Using SubClasses in admins create either not handable translation ids or urly urls

[BA-JBI]

Problem

Rererring to:
https://symfony.com/bundles/SonataAdminBundle/current/reference/advanced_configuration.html#inherited-classes

Variant A

App\Admin\ExampleAdmin:
    tags:
        -   name:            sonata.admin
#            [...]
    calls:
      - ['setSubClasses', [{
             class_a: App\Entity\SubClassA,
             class_b: App\Entity\SubClassB
      }]]

Is resulting in

Those translation labels are not great to handle

---

Variant B

App\Admin\ExampleAdmin:
    tags:
        -   name:            sonata.admin
#            [...]
    calls:
      - ['setSubClasses', [{
             app.my_class.subclass.class_a: App\Entity\SubClassA,
             app.my_class.subclass.class_b: App\Entity\SubClassB
      }]]

creates nice translation labels but ugly create url:

https://my.app.example/admin/entity/namespace/create?subclass=app.my_class.subclass.class_a

---

My suggested solution:

SonataAdminBundle/src/Resources/views/Button/create_button.html.twig

Line 25 in 75d7116

{{ 'link_action_create'|trans({}, 'SonataAdminBundle') }} {{ subclass|trans({}, admin.translationdomain) }}

Change to:

                    {{ 'link_action_create'|trans({}, 'SonataAdminBundle') }} {{ admin.translationLabel(subclass,'subclass')|trans({}, admin.translationDomain) }}

[VincentLanglet]

That would be a BC break and would require a new major version.
Doesn't seems worth it.