Thanks to @notnoop for this UX improvement suggestion.
The allocation’s task group is always known, so it
might as well be preselected in the sidebar when the
exec window opens. Also, if the task group only has
one task, might as well preselect it too.
This fixes a bug in #7815 where you can’t open an exec window from
the allocation overview because accessing `allocation.job.plainId`
fails across the proxied relationship.
This connects Xterm.js to a Nomad exec websocket so people
can interact on clients via live sessions. There are buttons on
job, allocation, task group, and task detail pages that open a
popup that lets them edit their shell command and start a
session.
More is to come, as recorded in issues.
