Display a sum of the SUs across currently-filtered jobs in the Job List view

[matthew-li]

Is your feature request related to a problem? Please describe.
Users sometimes wish to see the total number of service units used across a subset of their jobs (as opposed to the total used during the current period, which is already available on the Allocation Detail view).

Describe the solution you'd like
Render the sum of SUs across the currently-filtered jobs on the Job List view.

Additional context (Optional)

• This may affect page load time, especially when the number of jobs is large.
  • It doesn't make sense to render the sum when a superuser is viewing all jobs across all projects (and maybe in other cases).
  • A simple approach might be to set some threshold after which we won't compute the sum. The user could download the CSV and sum it themselves.
  • Other ideas are welcome.