[D&D] Aggregation service and Viz class research spike

[joshuarrrr]

After the Expressions Research spike, the current Viz service design utilizes a lot of the existing Visualize app's functions. This would let us easily support a lot of the existing visualizations features and even perhaps allow us to migrate exiting visualizations to use D&D. But to utilize it better we need to have a research spike on the AggService and the Viz class as these are responsible for translating the aggregation logic into the visualizations.

[ashwin-pc]

The spike is complete. Closing the issue

[joshuarrrr]

In the future for this type of research spike, it would be helpful to have some sort of written artifact we can later reference or add to developer docs.