Fix error description formatting for NotFoundHttpException in EntityValueResolver

[rela589n]

The value resolver provided by symfony (Symfony\Bridge\Doctrine\ArgumentResolver\EntityValueResolver) throws NotFoundHttpException when entity is not found:

if (null === $object && !$argument->isNullable()) {
    throw new NotFoundHttpException(sprintf('"%s" object not found by "%s".', $options->class, self::class).$message);
}

As the result, ApiExceptionFormatterListener formats response with following description:

{
    "error": "resource_not_found",
    "errorDescription": "\"App\\Entity\\MyEntity\" object not found by \"Symfony\\Bridge\\Doctrine\\ArgumentResolver\\EntityValueResolver\"."
}

It doesn't seem to be secure this way, and it would make sense to use generic resource_not_found_exception_message instead.

[fre5h]

@rela589n There is an error with uploading code coverage. I will fix it, then merge this request.