it would be handy to have a passthrough parameter to dd.concat - currently the union_categoricals call is parameter-free:

    dtype = "category"
            if left is not None and right is not None:
                dtype = union_categoricals(
                    [left.astype("category").values, right.astype("category").values]
                ).dtype

This can be made more fle

Description of the desired feature

The function uses np.min and np.max to get the bounding region of the given set of coordinates. This doesn't work if the coordinates are coming from xarray because the min