Expose the node alignment property for Sankey plots

[adamreeve]

Fixes #1938

This is based on the changes linked in the comment at #1938 (comment), which I've updated to work with the current code.

[archmoj]

🏆
LGTM.
Over to @alexcjohnson and @antoinerg

[alexcjohnson]

Great! So this works with the @plotly/d3-sankey we already have, doesn't need upstream changes?

Has this been tested with circular links in the diagram? Can we maybe add one mock showing this?

[adamreeve]

Yes the nodeAlign method is already in @plotly/d3-sankey so this doesn't need changes anywhere else.

This should also work with circular links, and actually the original changes I linked to above had a test mock using circular links so I will add that back in.

[adamreeve]

I'm not sure why the baseline test is now failing for some mocks when it was passing previously, the failing mocks aren't ones I've added.

[archmoj]

I'm not sure why the baseline test is now failing for some mocks when it was passing previously, the failing mocks aren't ones I've added.

There is a bug in our parallel image test now. To avoid that please rename your new mock and baseline to start with letter zz- to run in the end of process.
Thank you!

[adamreeve]

Thanks, looks like that fixed it!

[alexcjohnson]

💃 Great! Very well done @adamreeve!