Added some error handling which reverts the frontend data changes &
notifies the user

Does not remove the issue from the selected tab when it it de-selected, it instead gets purged when changing tab

Changed what is hidden when data is loading

Adds issues to list on frontend - need to push to backend

Submit button disables/enables
Submit button selects ids - but does not push it yet

Possibly need to change masonry library but so far it is the only one I found that works well

This removes the backlog list & instead creates a modal window that will
list all issues that are not part of a list for easy adding onto the
board

Closes #26205

Changed CSS transition property for only values that change

- Adds animation when opening & closing the sidebar
- Adds an animation when dragging boards to a new position
- Adds animations to dragging issues around

When opening the sidebar it will also animate the scrollLeft property to
make moving to the opened issue less blunt.

Closes #25630

With border board lists (those created from labels) the top border
created bad visual artifacts with the .board-inner gray border.
With this change the colored border overflows the padding-box of
.board-inner and extends to the edges.
It works very well with most colors, excepts for very light ones (such
as `#ff0` yellow for instance).

Fixes an issue in Safari that stops issues from being draggable

Closes #23048

Changed return statement instead of if
Delete objects after issue is closed

Added indicator when issue detail is visible

Need to get working the subscription
Styling updates

Changed how the data is passed into Vue resource

This was causing issues with moving from the done list

Closes #21219