- Request::get() (removed in Symfony 8): App\Utils\RequestParameter::get()
  keeps the same lookup (route, query, posted data) where the source is not
  certain; route attributes used directly for the admin id and _route.
- Validation constraints configured with named arguments instead of option
  arrays; Url requireTld and UrlType default_protocol explicit (current
  values kept, their defaults change in Symfony 8).
- UserChecker::checkPostAuth() token argument; eraseCredentials() no longer
  used (the plain password is cleared by UserFieldsUpdater).
- #[MapEntity] for the {slug} routes, Doctrine controller auto mapping off
  (removed from DoctrineBundle 3).
- Doctrine native lazy objects; ClassUtils replaced.
- PHP routing files instead of the XML ones (Sonata Admin, Sonata Media,
  profiler, errors), Payum YAML routing.
- Explicit property_info.with_constructor_extractor, profiler serializer
  data, Liip Imagine lazy Twig mode, translation_domain instead of
  label_catalogue, Lexik fallback locales from the framework.
- AdminExportTest: dates computed from the current date normalised.