Dendrogram: Allow using a categorical dimension to align to

[flying-sheep]

Is your feature request related to a problem? Please describe.

In this matplotlib example, the leaf level of the dendrogram points to the centers of groups defined by a categorical dimension:

Describe the solution you'd like

It should be possible to define the leaf level of the dendrogram operation instead of being confined to going all the way to the individual datum.

Describe alternatives you've considered

N/A