New in Symfony 4.3: Deprecating service aliases

Contributed by Joost van Driel and Renan in #29968. Deprecations are the key of our backward compatibility promise, which ensures smooth upgrades of your projects between minor versions (e.g. from 4.0 to 4.x). In order to provide a great developer experience, your own Symfony apps can also deprecate services, deprecate config options and even deprecate…