Add scheduled grading run details table

[Xiangmingchen]

https://user-images.githubusercontent.com/31719253/112406020-654ce300-8ce1-11eb-821c-d1b4a20fee8f.mp4

Features added

• Add "details" button to each scheduled run. Both staff and admin can see this button (unlike "edit")
• When clicked, a table shows up underneath with all student grading jobs' information
• Each grading job has netid, job id, check status button, and check log button
• [Unrelated] Added spinner when log is loading

Broadway endpoint integration

Used grading run env endpoint to pair up student netids and grading job ids (thanks to @st-arry for creating the endpoint 🎉). Because this endpoint is guarded by admin tokens, on-demand server acts as a middle man to relay the request results.

[Xiangmingchen]

Note that the getJobStatus function used by "status" button (in details table) gets the grading job status of all jobs within the run. This is because broadway doesn't have an endpoint for querying job status for a specific job. This might cause some performance issues given that a run might have hundreds of jobs in it.

However we shouldn't try to cache the result and reuse it every time because the grading job status might change between clicks. The best way to improve this would require a new endpoint on broadway.

[Xiangmingchen]

Address #69