[UPMERGE] 2.0 -> 2.1 (#423)

This PR has been generated automatically.
For more details see
[upmerge_pr.yaml](/Sylius/InvoicingPlugin/blob/1.0/.github/workflows/upmerge_pr.yaml).

**Remember!** The upmerge should always be merged with using `Merge pull
request` button.

In case of conflicts, please resolve them manually with usign the
following commands:
```
git fetch upstream
gh pr checkout <this-pr-number>
git merge upstream/2.1 -m "Resolve conflicts between 2.0 and 2.1"
```

If you use other name for the upstream remote, please replace `upstream`
with the name of your remote pointing to the `Sylius/InvoicingPlugin`
repository.

Once the conflicts are resolved, please run `git merge --continue` and
push the changes to this PR.

Author: TheMilek

ecs.php

@@ -23,11 +23,10 @@
     $config->import('vendor/sylius-labs/coding-standard/ecs.php');
 
     $config->parallel();
-    $config->paths(['src', 'spec']);
+    $config->paths(['src', 'tests/DependencyInjection', 'tests/Unit', 'tests/Behat']);
     $config->skip([
         InlineDocCommentDeclarationSniff::class . '.MissingVariable',
         InlineDocCommentDeclarationSniff::class . '.NoAssignment',
-        VisibilityRequiredFixer::class => ['*Spec.php'],
         '**/var/*',
         'src/Migrations/*',
     ]);

phpstan.neon

@@ -18,4 +18,5 @@ parameters:
         - '/Method Sylius\\InvoicingPlugin\\[a-zA-Z\\]+::getFlashBag\(\) should return Symfony\\Component\\HttpFoundation\\Session\\Flash\\FlashBagInterface but returns Symfony\\Component\\HttpFoundation\\Session\\SessionBagInterface\./'
         - '/Method Sylius\\InvoicingPlugin\\Security\\Voter\\InvoiceVoter::supports\(\) has parameter \$attribute with no typehint specified./'
         - '/Method Sylius\\InvoicingPlugin\\Security\\Voter\\InvoiceVoter::supports\(\) has parameter \$subject with no typehint specified./'
+        - '/Call to method scalarNode\(\) on an unknown class Symfony\\Component\\Config\\Definition\\Builder\\NodeBuilder<Symfony\\Component\\Config\\Definition\\Builder\\ArrayNodeDefinition>./'
         - '/expects string, string\|null given\.$/'