Add itemDecoration to checkbox groups nad radio groups to add borders to checkboxes and radio buttons

[freemansoft]

Connection with issue(s)

Close #1343

Connected to #???

Solution description

This change adds a BoxDecoration property called itemDecorator to FormBuilderCheckboxGroup and FormBiulderRadioGroup that is passed to every item they build. This lets you add borders to checkbox items and radio buttons.

1. Inter-control spacing is still set via the wrapSpacing property.
2. Intra-control margins on the side opposite the control (radio or checkbox) need to be set if the label is text only and a box is applied. There is no parameter for this. I looked at using wrapSpacing but that was a hack. The work around is to add trailing spaces to the label text :-(

Screenshots or Videos

This screenshot shows the changes to the example program. I deliberately showed the default behavior for text when a border is applied.

To Do

• Read contributing guide
• Check the original issue to confirm it is fully satisfied
• Add solution description to help guide reviewers
• Add unit test to verify new or fixed behaviour
• If apply, add documentation to code properties and package readme

[freemansoft]

Pushed change that removed unused dart:ui import

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e518c0e) 85.14% compared to head (dde086c) 87.03%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1344      +/-   ##
==========================================
+ Coverage   85.14%   87.03%   +1.88%     
==========================================
  Files          21       21              
  Lines         734      748      +14     
==========================================
+ Hits          625      651      +26     
+ Misses        109       97      -12     

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