Add additional grouping methods (other than strata) for boxplot visualizations

[joaopfonseca]

Describe the workflow you want to enable

Add a way to do grouping, over single or multiple features, on top of strata. So people could visualize groups from a "global"/aggregate point of view, or groups within strata.

Describe your proposed solution

Make the strata boxplots visualization implementation more flexible.

Describe alternatives you've considered, if relevant

No response

Additional context

No response