[R/wbStyle] remove the remaining parts of wbStyle

[JanMarvin]

It's highly unfortunate that so much of your time went into tweaking and cleaning this @jmbarbone , but hopefully I've told you early enough that it had no future. This thing is a monster that was awfully complex and the benefits of having it in openxlsx are getting fewer and fewer.

Header styling is no longer possible (it's possible working with wbWorkbook, but not in write.xlsx). Borders are possible, but they are lacking a user facing function, right now the user would have to create for each border cell the required border and cell style. Once we create a new add_style function, that creates a cell style swiftly and with style, the entire conversion should be done. Right now I just wanted to clean up the code and avoid having other users playing around with this, even though it is gone.

[JanMarvin]

Codecov Report

Merging #103 (3ac7fc9) into main (3b6ca04) will increase coverage by 4.64%.
The diff coverage is 9.67%.

@@            Coverage Diff             @@
##             main     #103      +/-   ##
==========================================
+ Coverage   51.34%   55.98%   +4.64%     
==========================================
  Files          42       40       -2     
  Lines        8419     7498     -921     
==========================================
- Hits         4323     4198     -125     
+ Misses       4096     3300     -796     

Impacted Files	Coverage Δ
R/asserts.R	56.25% <ø> (-11.10%)	⬇️
R/class-comment.R	77.08% <ø> (ø)
R/class-workbook-wrappers.R	31.60% <ø> (+0.53%)	⬆️
R/class-workbook.R	50.34% <ø> (+8.98%)	⬆️
R/conditional_formatting.R	0.00% <ø> (ø)
R/helperFunctions.R	78.15% <ø> (+51.80%)	⬆️
R/wb_styles.R	33.94% <0.00%> (-3.87%)	⬇️
R/writeData.R	76.13% <ø> (+0.58%)	⬆️
R/writeDataTable.R	75.00% <ø> (+6.25%)	⬆️
R/writexlsx.R	33.19% <ø> (+0.11%)	⬆️
... and 4 more

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[jmbarbone]

😢

But at least it gives us room to completely redo adding/creating styles. Ground-up redo will gives us a lot more room. The formatting is definitely one of openxlsx's strongest advantages but the backend left something to be desired. I just prettied up some of it -- so no a lot lost there/

And this increases our code coverage!

[JanMarvin]

😄 well fortunately I still know a few places where we could increase our coverage that do not require removing 3k loc!

Style objects are nice, I do not try to invalidate this argument, but they were constructed inefficient and hard to improve. Fortunately a lot of the internal handling is now already covered: conditional formatting, comment styles and number formats.

For cell styling there are already examples in the style manager and in the style vignette. We already have a lot covered, but it's ofc still a bit edgy to use and some friendly add_style() easing the burden is still required.

Borders are currently the thing frightening me the most (they require a lot of tedious cell construction and that usually isn't fun. There are reasons, why even in Excel the handling is no fun.