yiisoft
Set default `$currentOrder` in `Sort` class
$currentOrder can be set to default value after normalizing config.
https://github.com/yiisoft/data/blob/15ddd6e3bbb58bc7e341e173b0b66a51936dcecc/src/Reader/Sort.php#L114-L126
This will help avoid an exception if $currentOrder is not set manually.
https://github.com/yiisoft/data/blob/15ddd6e3bbb58bc7e341e173b0b66a51936dcecc/src/Paginator/KeysetPaginator.php#L444-L446
Order in Sort object is field name + order direction, e. g. "id asc". Configuration may contains a lot of fields, how we can understand which field should use by default?
For set default order we should select field also, not only direction. How we can understand which field should use by default?
For example, configuration: ['id' => ..., 'name' => ..., 'create_date' => ...]. Order may be id asc or create_date asc or name asc ...
If we use KeysetPaginator, then sorting is required. In case $currentOrder is not set, we can use the first field from the configuration. If multiple fields are required for sorting, the user must initialize $currentOrder.
