Parametric Masking: Apply Feathering and Blurring AFTER Mask Opacity and Mask Contrast

Is your feature request related to a problem? Please describe.
When using parametric masking, a great feature are the last four sliders in the panel: [Feathering and Blurring] and [Opacity and Contrast]. These are great and powerful tools, but as far as I can tell, Opacity and Contrast being applied after feathering and blurring does not make a lot of sense. What I see is that these two (Opacity and Contrast), when set far from 0, destroy the benefit, in terms of smoothness, achieved by the previous two adjustments (Feathering and Blurring).

Describe the solution you'd like
To invert the order in which these set of adjustments are applied: Apply first [Opacity and Contrast], and only then apply [Feathering and Blurring].

Alternatives
This would make interface more crowded, but there could be a dropdown similar to the existing one (Input after blur, ... etc.) to choose also the order of Opacity and Contrast in relation to the other two.

Additional context
When pushing Opacity or Contrast, the smoothness of the mask is drastically worsen, resulting in localized spots, or uneven masking that leads to artifacts or unusable results of the module. This might be less noticeable when applying small adjustment, but sometimes you just need to push the modules, and it's a pity to be limited just by this behavior when everything else is already set to get the job done.

Start by locating darktable's parametric masking implementation and the code paths for the Feathering, Blurring, Opacity, and Contrast controls. Trace the current mask-operation order, then verify that opacity and contrast precede feathering and blurring without introducing localized spots or uneven edges.