Automated test towards PHPStan level 6 (#5230)

* Automated test towards PHPStan level 6
Contributes to https://github.com/FreshRSS/FreshRSS/issues/4112
With this automated tests, files that are passing Level 6 are tested to avoid regressions towards Level 5 (which is the current baseline for the whole code-base)

It is included when calling `make test-all` or can be called specifically by `composer run-script phpstan-next`

* Test and example with 3 new passing files

1 files changed, 93 insertions, 0 deletions

diff --git a/tests/phpstan-next.txt b/tests/phpstan-next.txt
new file mode 100644
index 000000000..7f8d5e4e4
--- /dev/null
+++ b/tests/phpstan-next.txt
@@ -0,0 +1,93 @@
+# List of files, which are not yet passing PHPStan level 6 https://phpstan.org/user-guide/rule-levels
+# https://github.com/FreshRSS/FreshRSS/issues/4112
+# Used for automated tests to avoid regressions in files already passing that level.
+# Can be regenerated with something like:
+# find . -type d -name 'vendor' -prune -o -name '*.php' -exec sh -c 'vendor/bin/phpstan analyse --level 6 --memory-limit 512M {} >/dev/null 2>/dev/null || echo {}' \;
+
+./app/Controllers/extensionController.php
+./app/Controllers/feedController.php
+./app/Controllers/indexController.php
+./app/Controllers/updateController.php
+./app/Controllers/userController.php
+./app/Exceptions/AlreadySubscribedException.php
+./app/Exceptions/BadUrlException.php
+./app/Exceptions/FeedNotAddedException.php
+./app/Exceptions/ZipException.php
+./app/install.php
+./app/Mailers/UserMailer.php
+./app/Models/Auth.php
+./app/Models/BooleanSearch.php
+./app/Models/Category.php
+./app/Models/CategoryDAO.php
+./app/Models/CategoryDAOSQLite.php
+./app/Models/ConfigurationSetter.php
+./app/Models/Context.php
+./app/Models/DatabaseDAO.php
+./app/Models/DatabaseDAOPGSQL.php
+./app/Models/DatabaseDAOSQLite.php
+./app/Models/Entry.php
+./app/Models/Feed.php
+./app/Models/FeedDAO.php
+./app/Models/FeedDAOSQLite.php
+./app/Models/FilterAction.php
+./app/Models/FormAuth.php
+./app/Models/Log.php
+./app/Models/ReadingMode.php
+./app/Models/Search.php
+./app/Models/Share.php
+./app/Models/TagDAO.php
+./app/Models/TagDAOSQLite.php
+./app/Models/Themes.php
+./app/Models/UserDAO.php
+./app/Models/View.php
+./app/Services/ExportService.php
+./app/Services/ImportService.php
+./cli/_cli.php
+./cli/_update-or-create-user.php
+./cli/check.translation.php
+./cli/i18n/I18nCompletionValidator.php
+./cli/i18n/I18nData.php
+./cli/i18n/I18nFile.php
+./cli/i18n/I18nUsageValidator.php
+./cli/i18n/I18nValidatorInterface.php
+./cli/i18n/I18nValue.php
+./cli/manipulate.translation.php
+./lib/core-extensions/Google-Groups/extension.php
+./lib/core-extensions/Tumblr-GDPR/extension.php
+./lib/favicons.php
+./lib/http-conditional.php
+./lib/lib_date.php
+./lib/lib_install.php
+./lib/Minz/ActionController.php
+./lib/Minz/ActionException.php
+./lib/Minz/Configuration.php
+./lib/Minz/ConfigurationException.php
+./lib/Minz/ControllerNotActionControllerException.php
+./lib/Minz/ControllerNotExistException.php
+./lib/Minz/CurrentPagePaginationException.php
+./lib/Minz/Dispatcher.php
+./lib/Minz/Error.php
+./lib/Minz/Exception.php
+./lib/Minz/Extension.php
+./lib/Minz/ExtensionException.php
+./lib/Minz/ExtensionManager.php
+./lib/Minz/FileNotExistException.php
+./lib/Minz/FrontController.php
+./lib/Minz/Helper.php
+./lib/Minz/Log.php
+./lib/Minz/Mailer.php
+./lib/Minz/Migrator.php
+./lib/Minz/ModelArray.php
+./lib/Minz/ModelPdo.php
+./lib/Minz/Paginator.php
+./lib/Minz/Pdo.php
+./lib/Minz/PDOConnectionException.php
+./lib/Minz/PdoMysql.php
+./lib/Minz/PdoPgsql.php
+./lib/Minz/PdoSqlite.php
+./lib/Minz/PermissionDeniedException.php
+./lib/Minz/Request.php
+./lib/Minz/Session.php
+./lib/Minz/Translate.php
+./lib/Minz/Url.php
+./lib/Minz/View.php