Upgrade test application, old dependencies and make the code base ready for further improvement

.editorconfig

@@ -1,86 +1,25 @@
 root = true
 
 [*]
-# Change these settings to your own preference
 indent_style = space
 indent_size = 4
 
-# We recommend you to keep these unchanged
 end_of_line = lf
 charset = utf-8
 trim_trailing_whitespace = true
 insert_final_newline = true
 
 [*.feature]
-indent_style = space
-indent_size = 2
-
-[*.js]
-indent_style = space
-indent_size = 2
-
-[*.json]
-indent_style = space
 indent_size = 2
 
 [*.md]
-indent_style = space
-indent_size = 4
 trim_trailing_whitespace = false
 
-[*.neon]
-indent_style = tab
-indent_size = 4
-
-[*.php]
-indent_style = space
-indent_size = 4
-
 [*.sh]
 indent_style = tab
-indent_size = 4
 
 [*.{yaml,yml}]
-indent_style = space
-indent_size = 4
 trim_trailing_whitespace = false
 
-[.babelrc]
-indent_style = space
-indent_size = 2
-
-[.gitmodules]
-indent_style = tab
-indent_size = 4
-
-[.php_cs{,.dist}]
-indent_style = space
-indent_size = 4
-
-[composer.json]
-indent_style = space
-indent_size = 4
-
-[docker-compose{,.override}.{yaml,yml}]
-indent_style = space
+[{webpack.config.js,.eslintrc.js}]
 indent_size = 2
-
-[Dockerfile]
-indent_style = tab
-indent_size = 4
-
-[package.json]
-indent_style = space
-indent_size = 2
-
-[phpspec.yml{,.dist}]
-indent_style = space
-indent_size = 4
-
-[phpstan.neon]
-indent_style = tab
-indent_size = 4
-
-[phpunit.xml{,.dist}]
-indent_style = space
-indent_size = 4

.gitattributes

@@ -1,15 +1,20 @@
-/etc                        export-ignore
-/features                   export-ignore
-/spec                       export-ignore
-/tests                      export-ignore
-/.editorconfig              export-ignore
-/.gitattributes             export-ignore
-/.gitignore                 export-ignore
-/.scrutinizer.yml           export-ignore
-/.travis.yml                export-ignore
-/behat.yml.dist             export-ignore
-/easy-coding-standard.yml   export-ignore
-/phpspec.yml.dist           export-ignore
-/phpstan.neon               export-ignore
-/phpunit.xml.dist           export-ignore
-/README.md                  export-ignore
+/.editorconfig                      export-ignore
+/.gitattributes                     export-ignore
+/.github                            export-ignore
+/.gitignore                         export-ignore
+/CHANGELOG.md                       export-ignore
+/README.md                          export-ignore
+/UPGRADE.md                         export-ignore
+/behat.yml.dist                     export-ignore
+/composer-dependency-analyser.php   export-ignore
+/docs                               export-ignore
+/docs                               export-ignore
+/ecs.php                            export-ignore
+/etc                                export-ignore
+/infection.json.dist                export-ignore
+/node_modules                       export-ignore
+/phpunit.xml.dist                   export-ignore
+/psalm-baseline.xml                 export-ignore
+/psalm.xml                          export-ignore
+/rector.php                         export-ignore
+/tests                              export-ignore

.github/workflows/backwards-compatibility-check.yaml

@@ -0,0 +1,30 @@
+# See https://github.com/Roave/BackwardCompatibilityCheck
+
+name: "Backwards Compatibility Check"
+
+on:
+    pull_request: ~
+
+jobs:
+    backwards-compatibility-check:
+        name: "Backwards Compatibility Check"
+
+        runs-on: "ubuntu-latest"
+
+        steps:
+            -   name: "Checkout"
+                uses: "actions/checkout@v4"
+                with:
+                    fetch-depth: 0
+
+            -   name: "Setup PHP, with composer and extensions"
+                uses: "shivammathur/setup-php@v2"
+                with:
+                    php-version: "8.1"
+                    coverage: "none"
+
+            -   name: "Install tool"
+                run: "composer global require roave/backward-compatibility-check"
+
+            -   name: "Check for BC breaks"
+                run: "~/.composer/vendor/bin/roave-backward-compatibility-check --from=origin/${{ github.event.pull_request.base.ref }} --format=github-actions"