Add attributes to <ul>

Hi guys, any updates here?
Can somebody check my changes?
Thank you in advance

This is complex enough that others should mark it as RTBC..

Merge error!

@Igor Mashevskyi any plans to finish this?

@anybody I've resolved the merge error, so MR is mergeable now

Thanks! I guess what's finally needed now, are tests.

@grevil: Could you finally review this by time? Thanks!

Hey! First of all thanks for the contribution!

I'm currently reviewing the MR and I think this modules should provide attribute for the menu links (which covers the <li> and the <a> elements. I don't see big reasons to allow site managers to add attributes to the <ul> element itself and those could be rather added via a dedicated menu.html.twig file.

What do you think?

Sometimes it's important to add a class to a menu list element without coding, so I believe this would be a valuable improvement.
So, can somebody check my changes?
Thank you in advance

When I apply the patch, update the db and add a new link, I get the following error:

TypeError: _menu_link_attributes_add_attributes(): Argument #2 ($options) must be of type array, null given, called in /var/www/html/web/modules/custom/menu_link_attributes/menu_link_attributes.module on line 36 in _menu_link_attributes_add_attributes() (line 47 of modules/custom/menu_link_attributes/menu_link_attributes.module).

Feedback from @thomas.frobieter: Fine to merge this once ready.