Converts Validator constrains violations to a simple key => value array (field => error messages)

ConstraintViolationHelper.php

<?php

class ConstraintViolationHelper
{
    /**
     * Gets the validator errors.
     */
    public static function toArray(ConstraintViolationListInterface $violations): ?array
    {
        $errors = null;

        // loops through all violations and stores only their message
        foreach ($violations as $violation) {
            $errors[$violation->getPropertyPath()][] = $violation->getMessage();
        }

        return $errors;
    }
}