[php-slim4] Migrate from deprecated PHPUnit config schema
Created by: ybelenko
Is your feature request related to a problem? Please describe.
Current phpunit.xml.dist contains deprecated schema as it says:
$ composer test
> phpunit
PHPUnit 9.5.4 by Sebastian Bergmann and contributors.
Warning: Your XML configuration validates against a deprecated schema.
Suggestion: Migrate your XML configuration using "--migrate-configuration"!Describe the solution you'd like
Migrate to new config schema.