Make UserList more keyboard accessible

[t3chguy]

It should probably be a listbox widget with arrow-keys for navigation within the widget to not introduce N tabstops to the application.

[jugglinmike]

The MemberList component currently has two distinct lists of members: joined members and invited members. Should we:

• Include both in a single ListBox? If so, I think we'll move the list expansion buttons (labeled "and N others...") out of the document focus ring and instead make it reachable via ListBox navigation
• Implement each as distinct ListBoxes? In this case, should the list expansion buttons remain in the document focus ring?

The current interface design tends to suggest the first option because both lists share a single vertical scroll bar and because both lists are subject to the same search filter. I don't want to make any assumptions, though.

[t3chguy]

Based on #983 the underlying interaction may be changing anyhow

[jugglinmike]

Drat. Does that issue obviate this one? That one is much older; would you happen to know if anyone is working on it? Should I give it a shot, instead?

[t3chguy]

I will run a quick query by design early next week for any preliminary plans for the right panel and will get back to you

[jugglinmike]

Thanks!

[pvagner]

If the question is still relevant today, I'd say we would like to have single list with keyboard and focus handling identical to room list.
Joined Members and Invited members should be list items with aria-level set to 0 and the member tiles should be list items with aria-level set to 1.
When member list tiles have focus up / down / home /end change the focus, enter activates focused item.
When either joined members item or invited members item has keyboard focus it should be possible to use the same set of navigation keys and also left arrow key to collapse and right arrow key to expand. Whether a node is expanded should be communicated by using aria-expanded property.
I'd like to have the same ux we do have with the room list.
Hopefully I haven't forgotten something important.
Thank you.

[t3chguy]

Blocked on #983