Simplified interface, PHP 8 attributes

New Requirements

None

New features

• Added HandlerProviderWithChain, which allows chaining multiple handler providers. They are
  queried in turn until a handler is found.
• Handlers, Permissions, and Voters can now be defined using PHP 8 attributes instead of YAML. Added
  MessageBusPassWithAttributes, and the attributes Handler, Permission, and Vote.

Backward Incompatible Changes

• HandlerProvider::getHandlerForMessage() can now return null, undefined handlers are handled in
  one single location now, that is DispatcherWithHandlerProvider.
• Dropped HandlerProviderPass, CommandDispatcher, CommandHandlerProvider,
  CommandHandlerProviderPass, QueryDispatcher, QueryHandlerProvider,
  QueryHandlerProviderPass in favor of MessageBusPass.
• Dropped ContainerHandlerProvider in favor of HandlerProviderWithContainer.
• Dropped AssertingDispatcher in favor of RestrictedDispatcher.
• Dropped SimpleHandlerProvider in favor of HandlerProviderWithHandlers.
• Dropped SimpleDispatcher in favor of DispatcherWithHandlerProvider.
• Dropped NotFound in favor of HandlerNotFound.

Deprecated Features

None

Other Changes

None