[Admin] adding new shipping category

[loicginoux]

Summary

This PR migrates the creation of new shipping categories to the new admin interface.
It follows the same kind of work done for Tax categories in #5674
There is no issue but a project item that I cannot move or comment, probably due to permission issues. Solidus Admin (view)

I also fixed searching shipping categories. This was a feature not present on old admin and by introducing new UI, and capability to search them, it was missing a ransack config to allow searching them by name.

Screen.Recording.2024-04-10.at.13.00.01.mov

Checklist

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[kennyadsl]

Thanks @loicginoux! I created #5720 to attach to this PR, thanks again!

[loicginoux]

Not sure about the failing linter CI step. Should I look into it or is it something with the CI ? The error does not look like specific to this PR...

[kennyadsl]

The error seems to be related to ESLint in the CI. I you want to take a look at it with another PR, you are more than welcome, thanks Loic!

[tvdeyen]

Thanks. ES lint error is handled in #5722

[loicginoux]

I just rebased branch from main after the linting CI error has been fixed in #5721. CI should be green here after that.

[codecov]

Codecov Report

Attention: Patch coverage is 97.29730% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 88.86%. Comparing base (3f6c58c) to head (55ec39e).

Files	Patch %	Lines
...rs/solidus_admin/shipping_categories_controller.rb	96.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5718      +/-   ##
==========================================
+ Coverage   88.84%   88.86%   +0.02%     
==========================================
  Files         704      705       +1     
  Lines       16757    16789      +32     
==========================================
+ Hits        14887    14919      +32     
  Misses       1870     1870              

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