Issue #97, #98: Aggregate job info per day and per week as part of JobPr...

...ocessing Step in the ETL. Also enable a rest api to fetch this aggregated app info
It is very confusing to call this runId.
This appears to suggest that we aggregate data within a run, which we don't.
We aggregate up to a day or week. So this field is a day or week.
aggregationId may be better, with explanation this could be a day, week, month, or whatever we want to agg by.
The fact that we end up getting this value by rounding down runId (which happen to be timestamps when the flow started)
is a slightly different story.

We do by the way need to clearly describe that all jobs in a flow get aggregated to the start of the first job
or the timestamp when the flow is submitted or something like that.
I can imagine that people might be confused what happens when a flow spans more than one day.