UPGRADE FROM 5.0 to 5.1
=======================
EventDispatcher
---------------
* Deprecated `LegacyEventDispatcherProxy`. Use the event dispatcher without the proxy.
FrameworkBundle
* Deprecated passing a `RouteCollectionBuiler` to `MicroKernelTrait::configureRoutes()`, type-hint `RoutingConfigurator` instead
HttpFoundation
--------------
* Deprecate `Response::create()`, `JsonResponse::create()`,
`RedirectResponse::create()`, and `StreamedResponse::create()` methods (use
`__construct()` instead)
Notifier
--------
* [BC BREAK] The `ChatMessage::fromNotification()` method's `$recipient` and `$transport`
arguments were removed.
* [BC BREAK] The `EmailMessage::fromNotification()` and `SmsMessage::fromNotification()`
methods' `$transport` argument was removed.
Routing
-------
* Deprecated `RouteCollectionBuilder` in favor of `RoutingConfigurator`.