(Towards #2381) Re-structure classes for reduction nodes.

[arporter]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.95%. Comparing base (a7b7d27) to head (98492a6).
⚠️ Report is 38 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3333      +/-   ##
==========================================
- Coverage   99.95%   99.95%   -0.01%     
==========================================
  Files         384      386       +2     
  Lines       54271    54187      -84     
==========================================
- Hits        54249    54165      -84     
  Misses         22       22              

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[arporter]

It looks like the Met Office has removed one of the pages that the tutorial used to point to so I've updated the link.
Ready for another look now.

[arporter]

This time, the link-check failure is for a perfectly valid Issue on github so I think we can safely ignore it.

[LonelyCat124]

Hi @arporter,

I'm not quite satisfied with the xfailing test - see inline.

[arporter]

Ready for another look/discussion about the test.

[LonelyCat124]

Set CI running, otherwise I think everything is resolved.

[LonelyCat124]

CI passed, ready to merge.