Pivot tables

This adds support to summarize any <Table that uses list/filter endpoint with an Excel-like pivot table. It uses the endpoint described in grin-global-server#548.

The API is documented in grin-global-server#548.

UI

We add a Pivot tab uses a new pivot view and opens a dialog where the user selects the fields to group by and the fields to be aggregated. The filters and pagination stay the same, except that sorting will only use fields in group-bys and aggregations. The pivot table configuration dialog can be re-opened with the FAB button.

The pivot configuration dialog mimics the one users know: Group By fields are on the left, aggregations on the right.

After applying the pivot config and calling the API endpoint, the UI reconstructs, based on the PivotRequest, a tabular display of the response from the API. For example:

• The number of elements in the $.123.SD array is 2, resulting in a rowSpan += 2
• The number of keys in $.123 is also two, resulting in rowSpan += 2 = 4 for site = 123.