After the updating to >= v.4.21.0 i noticed that my current solution to add background classes to my cells stopped working. I noticed in the updated the code, that adding custom attributes seems to be adding a ";" (semi-colon). This seems to interupt with my current code.
I also noticed in your example code for cell render, that it works like this (and it only uses "style" as adding custom attribute).
I have found a workaround for my given case, where i put whitespace both at the start and at the end of my class which i wish to add as an custom attribute.
I also noticed that everything gets added twice (probably because of pre-render), so is it possible to get "args.FirstRender" on "DataGridCellRenderEventArgs" as well? (it is currently present in "GroupRowRenderEventArgs").
If everything works as intended, ill just have to adapt to only using style instead i think.