Discussion: add title to multiple colorbars?

[LucaMarconato]

##
from spatialdata.datasets import blobs
import spatialdata_plot
import matplotlib.pyplot as plt

sdata = blobs()
sdata['blobs_polygons']['column'] = 0

(
    sdata.pl.render_images('blobs_image')
    .pl.render_shapes('blobs_circles', color='radius')
    .pl.render_shapes('blobs_polygons', color='column')
    .pl.show()
)
plt.show()

gives

Which looks great! But it may be confusing to know which colorbar refers to what. I would consider one of the following:

1. we leave it as it is: the user should use different colorbars (e.g. viridis + gray) when plotting multiple elements at the same time, so the ambiguity doesn't exist
2. we add a title on top of the colorbar to make clear what the colorbar refers to
3. we show only one colorbar maximum.

I prefer having multiple colorbar, so I'd choose either 1 or 2. @timtreis @Sonja-Stockhaus wdyt?

[timtreis]

Don't like 3) either.

Vaguely related to #349 in which I have to refactor the entire logic anyway. One option would be to add cbar_title to the individual calls

[timtreis]

Now possible with #518

from spatialdata.datasets import blobs
import spatialdata_plot
import matplotlib.pyplot as plt

sdata = blobs()
sdata["blobs_polygons"]["column"] = range(len(sdata["blobs_polygons"]))

# Default: column name becomes colorbar label automatically
(
      sdata.pl.render_images("blobs_image")
      .pl.render_shapes("blobs_circles", color="radius")
      .pl.render_shapes("blobs_polygons", color="column")
      .pl.show()
)

# Custom labels via colorbar_params
(
      sdata.pl.render_images("blobs_image")
      .pl.render_shapes("blobs_circles", color="radius", colorbar_params={"label": "Circle radius"})
      .pl.render_shapes("blobs_polygons", color="column", colorbar_params={"label": "Polygon ID"})
      .pl.show()
)