closing classes from accidental extension and symfony best practices

[dbu]

symfony recommends to not use parameters for the classes that implement services. i only kept the ones that are actually configurable. everything else should be done with service decorators or custom compiler passes if ever needed, to make things less implicit.

[dbu]

@WyriHaximus as you seem to use sculpin actively, do you maybe have input if i have been too agressive with making classes final? there are interfaces for pretty much everything, so it should be possible to proxy if only a small thing should be customized. a lot of things where protected but did not look suitable to extend

[WyriHaximus]

@dbu I'm all in favour of make everything (where possible) final 👍

[GwendolenLynch]

A vote in favour of this PR, especially for this:

-   <service id="sculpin_markdown_twig_compat.converter_listener" class="%sculpin_markdown_twig_compat.convert_listener.class%" public="true">
+   <service id="sculpin_markdown_twig_compat.converter_listener" class="Sculpin\Bundle\MarkdownTwigCompatBundle\ConvertListener" public="true">

@dbu This branch needs a rebase now, as some of my recent PRs have caused conflicts 😇

[dbu]

rebased and solved the conflicts. glad if we can merge this and #417 soon to not get into conflicts again ;-)